Three-dimensional memory device including a deformation-resistant edge seal structure and methods for making the same

ABSTRACT

A vertically alternating stack of insulating layers and dielectric spacer material layers is formed over a semiconductor substrate. The vertically alternating stack is patterned into a first alternating stack located at a center region of a memory die and a second alternating stack that laterally encloses the first alternating stack. Memory stack structures are formed through the first alternating stack, and portions of the dielectric spacer material layers in the first alternating stack are replaced with electrically conductive layers while maintaining the second alternating stack intact. At least one metallic wall structure is formed through the second alternating stack. An edge seal assembly is provided, which includes at least one vertical stack of metallic seal structures. Each vertical stack of metallic seal structures vertically extends contiguously from a top surface of the semiconductor substrate to a bonding-side surface of the memory die, and includes a respective metallic wall structure.

FIELD

The present disclosure relates generally to the field of semiconductordevices, and particular to a three-dimensional memory device including adeformation-resistant edge structure and methods of manufacturing thesame.

BACKGROUND

A three-dimensional memory device including three-dimensional verticalNAND strings having one bit per cell is disclosed in an article by T.Endoh et al., titled “Novel Ultra High Density Memory With AStacked-Surrounding Gate Transistor (S-SGT) Structured Cell”, IEDM Proc.(2001) 33-36.

SUMMARY

According to an aspect of the present disclosure, a three-dimensionalmemory device is provided including a memory die that comprises a firstalternating stack of first insulating layers and electrically conductivelayers located over a semiconductor substrate; memory stack structuresvertically extending through the first alternating stack and comprisingvertical stacks of memory elements; a second alternating stack of secondinsulating layers and spacer dielectric layers that laterally surroundsthe first alternating stack and located over the semiconductorsubstrate; memory-die bonding pads included in upper-level dielectricmaterial layers and located on a bonding-side surface of the memory die;and an edge seal assembly comprising at least one vertical stack ofmetallic seal structures, wherein each of the at least one verticalstack of metallic seal structures vertically extends contiguously from atop surface of the semiconductor substrate to the bonding-side surfaceof the memory die and comprises a respective metallic wall structurethat extends through the second alternating stack and laterally enclosesthe first alternating stack, wherein the second alternating stackcomprises multiple nested portions divided by the respective metallicwall structure.

According to another aspect of the present disclosure, a method offorming a three-dimensional memory device is provided. The methodcomprises forming a memory die using the processing steps of: forming avertically alternating stack of insulating layers and dielectric spacermaterial layers over a semiconductor substrate; patterning thevertically alternating stack into a first alternating stack of firstinsulating layers and sacrificial material layers and a secondalternating stack of second insulating layers and spacer dielectriclayers, wherein the second alternating stack laterally encloses, and islaterally spaced from, the first alternating stack; forming memory stackstructures comprising vertical stacks of memory elements through thefirst alternating stack; replacing the sacrificial material layers withelectrically conductive layers while retaining the second alternatingstack intact; forming at least one metallic wall structure verticallythrough the second alternating stack, wherein the at least one metallicwall structure divides the second alternating stack into multiple nestedportions; forming memory-die bonding pads within dielectric materiallayers over the first alternating stack; and forming an edge sealassembly comprising at least one vertical stack of metallic sealstructures, wherein each of the at least one vertical stack of metallicseal structures vertically extends contiguously from a top surface ofthe semiconductor substrate to a bonding-side surface of the dielectricmaterial layers, and comprises a respective one of the at least onemetallic wall structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a vertical cross-sectional view of a first exemplarystructure after formation of semiconductor devices, lower leveldielectric layers, lower metal interconnect structures, and in-processsource level material layers on a semiconductor substrate according to afirst embodiment of the present disclosure.

FIG. 1B is a top-down view of the first exemplary structure of FIG. 1A.The hinged vertical plane A-A′ is the plane of the verticalcross-sectional view of FIG. 1A.

FIG. 1C is a magnified view of the in-process source level materiallayers along the vertical plane C-C′ of FIG. 1B.

FIG. 2 is a vertical cross-sectional view of the first exemplarystructure after formation of a first-tier alternating stack of firstinsulating layers and first spacer material layers according to anembodiment of the present disclosure.

FIG. 3A is a vertical cross-sectional view of the first exemplarystructure after patterning a first-tier staircase region, a firstretro-stepped dielectric material portion, and an inter-tier dielectriclayer according to an embodiment of the present disclosure.

FIG. 3B is another vertical cross-sectional view of the first exemplarystructure of FIG. 3A.

FIG. 3C is a schematic plan view of an in-process memory die thatembodies the first exemplary structure of FIGS. 3A and 3B. The planeA-A′ is the plane of the vertical cross-sectional view of FIG. 3A, andthe plane B-B′ is the plane of the vertical cross-sectional view of FIG.3B.

FIG. 4A is a vertical cross-sectional view of the first exemplarystructure after formation of first-tier memory openings and first-tiersupport openings according to an embodiment of the present disclosure.

FIG. 4B is a horizontal cross-sectional view of the first exemplarystructure of FIG. 4A. The hinged vertical plane A-A′ corresponds to theplane of the vertical cross-sectional view of FIG. 4A.

FIG. 5 is a vertical cross-sectional view of the first exemplarystructure after formation of various sacrificial fill structuresaccording to an embodiment of the present disclosure.

FIG. 6 is a vertical cross-sectional view of the first exemplarystructure after formation of a second-tier alternating stack of secondinsulating layers and second spacer material layers, second steppedsurfaces, and a second retro-stepped dielectric material portionaccording to an embodiment of the present disclosure.

FIG. 7A is a vertical cross-sectional view of the first exemplarystructure after formation of second-tier memory openings and second-tiersupport openings according to an embodiment of the present disclosure.

FIG. 7B is a horizontal cross-sectional of the first exemplary structurealong the horizontal plane B-B′ of FIG. 7A. The hinged vertical planeA-A′ corresponds to the plane of the vertical cross-sectional view ofFIG. 7A.

FIG. 8 is a vertical cross-sectional view of the first exemplarystructure after formation of inter-tier memory openings and inter-tiersupport openings according to an embodiment of the present disclosure.

FIGS. 9A-9D illustrate sequential vertical cross-sectional views of amemory opening during formation of a memory opening fill structureaccording to an embodiment of the present disclosure.

FIG. 10A is a vertical cross-sectional view of the first exemplarystructure after formation of memory opening fill structures and supportpillar structures according to an embodiment of the present disclosure.

FIG. 10B is a horizontal cross-sectional of the first exemplarystructure along the horizontal plane B-B′ of FIG. 10A. The hingedvertical plane A-A′ corresponds to the plane of the verticalcross-sectional view of FIG. 10A.

FIG. 10C is another vertical cross-sectional view of first exemplarystructure of FIGS. 10A and 10B.

FIG. 11 is a vertical cross-sectional view of the first exemplarystructure after formation of a first contact-level dielectric layer, afirst sacrificial semiconductor layer, a guard ring trench, and a sourcecontact trench according to an embodiment of the present disclosure.

FIG. 12 is a vertical cross-sectional view of the first exemplarystructure after formation of a dielectric spacer material layer, asecond sacrificial semiconductor layer, and a first sacrificialdielectric layer according to an embodiment of the present disclosure.

FIG. 13 is a vertical cross-sectional view of the first exemplarystructure after simultaneous formation of backside trenches and crackstopper moat trenches according to an embodiment of the presentdisclosure.

FIG. 14 is a vertical cross-sectional view of the first exemplarystructure after formation of dielectric spacers at peripheries of thebackside trenches and the crack stopper moat trenches according to anembodiment of the present disclosure.

FIG. 15 is a vertical cross-sectional view of the first exemplarystructure after formation of sacrificial backside trench fillstructures, sacrificial moat trench fill structures, and a secondsacrificial dielectric layer according to an embodiment of the presentdisclosure.

FIG. 16 is a vertical cross-sectional view of the first exemplarystructure after patterning of the second sacrificial dielectric layerand removal of the sacrificial backside trench fill structures accordingto an embodiment of the present disclosure.

FIG. 17 is a magnified view of a region of a backside trench in thefirst exemplary structure of FIG. 16.

FIG. 18 is a vertical cross-sectional view of a region of the backsidetrench after formation of a source-level cavity according to anembodiment of the present disclosure.

FIG. 19 is a vertical cross-sectional view of a region of the backsidetrench after physically exposing bottom end portions of verticalsemiconductor channels according to an embodiment of the presentdisclosure.

FIG. 20 is a vertical cross-sectional view of a region of the backsidetrench after formation of a source semiconductor layer according to anembodiment of the present disclosure.

FIG. 21A is a vertical cross-section of the first exemplary structureafter formation of semiconductor oxide portions according to anembodiment of the present disclosure.

FIG. 21B is a magnified view of a region of the backside trench in thefirst exemplary structure of FIG. 21A.

FIG. 22A is a vertical cross-section of the first exemplary structureafter formation of backside recesses according to an embodiment of thepresent disclosure.

FIG. 22B is a magnified view of a region of the backside trench in thefirst exemplary structure of FIG. 22A.

FIG. 23A is a vertical cross-section of the first exemplary structureafter formation of electrically conductive layers according to anembodiment of the present disclosure.

FIG. 23B is a magnified view of a region of the backside trench in thefirst exemplary structure of FIG. 23A.

FIG. 24A is a vertical cross-section of the first exemplary structureafter removal of the first and second sacrificial dielectric layer and ahorizontal portion of the second sacrificial semiconductor layeraccording to an embodiment of the present disclosure.

FIG. 24B is a magnified view of a region of the backside trench in thefirst exemplary structure of FIG. 24A.

FIG. 25 is a vertical cross-section of the first exemplary structureafter removal of the sacrificial moat trench fill structures andvertical portions of the second sacrificial semiconductor layeraccording to an embodiment of the present disclosure.

FIG. 26 is a vertical cross-sectional view of the first exemplarystructure after removal of horizontal portions of the dielectric spacermaterial layer and the first sacrificial semiconductor layer accordingto an embodiment of the present disclosure.

FIG. 27 is a vertical cross-sectional view of the first exemplarystructure after formation of a source contact via structure and metallicwall structures according to an embodiment of the present disclosure.

FIG. 28 is a vertical cross-sectional view of the first exemplarystructure after formation of staircase-region contact via structuresaccording to an embodiment of the present disclosure.

FIG. 29 is a vertical cross-sectional view of the first exemplarystructure after formation of additional contact via structures accordingto embodiments of the present disclosure.

FIG. 30 is a vertical cross-sectional view of the first exemplarystructure after completion of formation of a memory die according to anembodiment of the present disclosure.

FIG. 31 is a vertical cross-sectional view of a support die according toan embodiment of the present disclosure.

FIG. 32 is a vertical cross-sectional view of the first exemplarystructure after bonding the support die to the memory die according toan embodiment of the present disclosure.

FIG. 33 is a plan view of the first exemplary structure of FIG. 32.

FIG. 34 is a vertical cross-sectional view of a second exemplarystructure after formation of memory opening fill structures according toan embodiment of the present disclosure.

FIG. 35 is a vertical cross-sectional view of the second exemplarystructure after formation of a first contact-level dielectric layer,support openings and a guard ring trench according to an embodiment ofthe present disclosure.

FIG. 36 is a vertical cross-sectional view of the second exemplarystructure after formation of dielectric spacers and support pillarstructures according to an embodiment of the present disclosure.

FIG. 37 is a vertical cross-sectional view of the second exemplarystructure after formation of a sacrificial guard ring trench fillstructure according to an embodiment of the present disclosure.

FIG. 38 is a vertical cross-sectional view of the second exemplarystructure after formation of a first sacrificial dielectric layer,backside trenches, and crack stopper moat trenches according to anembodiment of the present disclosure.

FIG. 39 is a vertical cross-sectional view of the second exemplarystructure after formation of temporary backside trench fill structuresand temporary moat trench fill structures according to an embodiment ofthe present disclosure.

FIG. 40 is a vertical cross-sectional view of the second exemplarystructure after formation of a second sacrificial dielectric layeraccording to an embodiment of the present disclosure.

FIG. 41 is a vertical cross-sectional view of the second exemplarystructure after removal of the temporary backside trench fill structuresaccording to an embodiment of the present disclosure.

FIG. 42 is a vertical cross-section of the second exemplary structureafter formation of backside recesses according to an embodiment of thepresent disclosure.

FIG. 43 is a vertical cross-section of the second exemplary structureafter formation of electrically conductive layers according to anembodiment of the present disclosure.

FIG. 44 is a vertical cross-section of the second exemplary structureafter removal of temporary moat trench fill structures according to anembodiment of the present disclosure.

FIG. 45 is a vertical cross-section of the second exemplary structureafter formation of dielectric spacers according to an embodiment of thepresent disclosure.

FIG. 46 is a vertical cross-sectional view of the second exemplarystructure after formation of sacrificial backside trench fill structuresand sacrificial moat trench fill structures according to an embodimentof the present disclosure.

FIG. 47 is a vertical cross-sectional view of the second exemplarystructure after formation of a sacrificial dielectric cover layer andremoval of the sacrificial backside trench fill structure and asource-level sacrificial layer according to an embodiment of the presentdisclosure.

FIG. 48 is a vertical cross-sectional view of the second exemplarystructure after deposition of a doped semiconductor material layeraccording to an embodiment of the present disclosure.

FIG. 49 is a vertical cross-sectional view of the second exemplarystructure after removal of a portion of the doped semiconductor materiallayer, the sacrificial dielectric cover layer, and the first sacrificialdielectric layer according to an embodiment of the present disclosure.

FIG. 50 is a vertical cross-sectional view of the second exemplarystructure after removal of the sacrificial moat trench fill structuresaccording to an embodiment of the present disclosure.

FIG. 51 is a vertical cross-sectional view of the second exemplarystructure after vertically recessing the doped semiconductor materiallayer according to an embodiment of the present disclosure.

FIG. 52 is a vertical cross-sectional view of the second exemplarystructure after formation of upper source contact via portions andmetallic wall structures according to an embodiment of the presentdisclosure.

FIG. 53 is a vertical cross-sectional view of the second exemplarystructure after formation of a second contact-level dielectric layer andstaircase-region contact via structures according to an embodiment ofthe present disclosure.

FIG. 54 is a vertical cross-sectional view of the second exemplarystructure after formation of additional contact via structures accordingto embodiments of the present disclosure.

DETAILED DESCRIPTION

As discussed above, the embodiments of the present disclosure aredirected to a three-dimensional memory device including adeformation-resistant edge structure and methods of manufacturing thesame, the various aspects of which are described herein in detail. Anedge seal is used to provide a protective barrier around a memory die ofa three-dimensional memory device. As the total number of word linesincreases in a three-dimensional memory device, deformation of memorydies increases, thereby increasing the difficulty in bonding or mountingof the memory dies. Various embodiments of the present disclosureprovide a memory die that includes a deformation-resistant edge seal.This configuration reduces distortion of a semiconductor die, such as amemory die, and enhances bonding between two semiconductor dies. Theembodiments of the present disclosure can be used to form varioussemiconductor devices such as three-dimensional monolithic memory arraydevices comprising a plurality of NAND memory strings.

The drawings are not drawn to scale. Multiple instances of an elementmay be duplicated where a single instance of the element is illustrated,unless absence of duplication of elements is expressly described orclearly indicated otherwise. Ordinals such as “first,” “second,” and“third” are used merely to identify similar elements, and differentordinals may be used across the specification and the claims of theinstant disclosure. The same reference numerals refer to the sameelement or similar element. Unless otherwise indicated, elements havingthe same reference numerals are presumed to have the same compositionand the same function. Unless otherwise indicated, a “contact” betweenelements refers to a direct contact between elements that provides anedge or a surface shared by the elements. As used herein, a firstelement located “on” a second element can be located on the exteriorside of a surface of the second element or on the interior side of thesecond element. As used herein, a first element is located “directly on”a second element if there exist a physical contact between a surface ofthe first element and a surface of the second element. As used herein, a“prototype” structure or an “in-process” structure refers to a transientstructure that is subsequently modified in the shape or composition ofat least one component therein.

As used herein, a “layer” refers to a material portion including aregion having a thickness. A layer may extend over the entirety of anunderlying or overlying structure, or may have an extent less than theextent of an underlying or overlying structure. Further, a layer may bea region of a homogeneous or inhomogeneous continuous structure that hasa thickness less than the thickness of the continuous structure. Forexample, a layer may be located between any pair of horizontal planesbetween, or at, a top surface and a bottom surface of the continuousstructure. A layer may extend horizontally, vertically, and/or along atapered surface. A substrate may be a layer, may include one or morelayers therein, or may have one or more layer thereupon, thereabove,and/or therebelow.

As used herein, a first surface and a second surface are “verticallycoincident” with each other if the second surface overlies or underliesthe first surface and there exists a vertical plane or a substantiallyvertical plane that includes the first surface and the second surface. Asubstantially vertical plane is a plane that extends straight along adirection that deviates from a vertical direction by an angle less than5 degrees. A vertical plane or a substantially vertical plane isstraight along a vertical direction or a substantially verticaldirection, and may, or may not, include a curvature along a directionthat is perpendicular to the vertical direction or the substantiallyvertical direction.

As used herein, a “memory level” or a “memory array level” refers to thelevel corresponding to a general region between a first horizontal plane(i.e., a plane parallel to the top surface of the substrate) includingtopmost surfaces of an array of memory elements and a second horizontalplane including bottommost surfaces of the array of memory elements. Asused herein, a “through-stack” element refers to an element thatvertically extends through a memory level.

As used herein, a “semiconducting material” refers to a material havingelectrical conductivity in the range from 1.0×10⁻⁵ S/m to 1.0×10⁵ S/m.As used herein, a “semiconductor material” refers to a material havingelectrical conductivity in the range from 1.0×10⁻⁵ S/m to 1.0 S/m in theabsence of electrical dopants therein, and is capable of producing adoped material having electrical conductivity in a range from 1.0 S/m to1.0×10⁷ S/m upon suitable doping with an electrical dopant. As usedherein, an “electrical dopant” refers to a p-type dopant that adds ahole to a valence band within a band structure, or an n-type dopant thatadds an electron to a conduction band within a band structure. As usedherein, a “conductive material” refers to a material having electricalconductivity greater than 1.0×10⁵ S/m. As used herein, an “insulatormaterial” or a “dielectric material” refers to a material havingelectrical conductivity less than 1.0×10⁻⁵ S/m. As used herein, a“heavily doped semiconductor material” refers to a semiconductormaterial that is doped with electrical dopant at a sufficiently highatomic concentration to become a conductive material either as formed asa crystalline material or if converted into a crystalline materialthrough an anneal process (for example, from an initial amorphousstate), i.e., to provide electrical conductivity greater than 1.0×10⁵S/m. A “doped semiconductor material” may be a heavily dopedsemiconductor material, or may be a semiconductor material that includeselectrical dopants (i.e., p-type dopants and/or n-type dopants) at aconcentration that provides electrical conductivity in the range from1.0×10⁻⁵ S/m to 1.0×10⁷ S/m. An “intrinsic semiconductor material”refers to a semiconductor material that is not doped with electricaldopants. Thus, a semiconductor material may be semiconducting orconductive, and may be an intrinsic semiconductor material or a dopedsemiconductor material. A doped semiconductor material can besemiconducting or conductive depending on the atomic concentration ofelectrical dopants therein. As used herein, a “metallic material” refersto a conductive material including at least one metallic elementtherein. All measurements for electrical conductivities are made at thestandard condition.

A monolithic three-dimensional memory array is one in which multiplememory levels are formed above a single substrate, such as asemiconductor wafer, with no intervening substrates. The term“monolithic” means that layers of each level of the array are directlydeposited on the layers of each underlying level of the array. Incontrast, two dimensional arrays may be formed separately and thenpackaged together to form a non-monolithic memory device. For example,non-monolithic stacked memories have been constructed by forming memorylevels on separate substrates and vertically stacking the memory levels,as described in U.S. Pat. No. 5,915,167 titled “Three-dimensionalStructure Memory.” The substrates may be thinned or removed from thememory levels before bonding, but as the memory levels are initiallyformed over separate substrates, such memories are not true monolithicthree-dimensional memory arrays. The substrate may include integratedcircuits fabricated thereon, such as driver circuits for a memory device

The various three-dimensional memory devices of the present disclosureinclude a monolithic three-dimensional NAND string memory device, andcan be fabricated using the various embodiments described herein. Themonolithic three-dimensional NAND string is located in a monolithic,three-dimensional array of NAND strings located over the substrate. Atleast one memory cell in the first device level of the three-dimensionalarray of NAND strings is located over another memory cell in the seconddevice level of the three-dimensional array of NAND strings.

Generally, a semiconductor package (or a “package”) refers to a unitsemiconductor device that can be attached to a circuit board through aset of pins or solder balls. A semiconductor package may include asemiconductor chip (or a “chip”) or a plurality of semiconductor chipsthat are bonded thereamongst, for example, by flip-chip bonding oranother chip-to-chip bonding. A package or a chip may include a singlesemiconductor die (or a “die”) or a plurality of semiconductor dies. Adie is the smallest unit that can independently execute externalcommands or report status. Typically, a package or a chip with multipledies is capable of simultaneously executing as many external commands asthe total number of dies therein. Each die includes one or more planes.Identical concurrent operations can be executed in each plane within asame die, although there may be some restrictions. In case a die is amemory die, i.e., a die including memory elements, concurrent readoperations, concurrent write operations, or concurrent erase operationscan be performed in each plane within a same memory die. In a memorydie, each plane contains a number of memory blocks (or “blocks”), whichare the smallest unit that can be erased by in a single erase operation.Each memory block contains a number of pages, which are the smallestunits that can be selected for programming. A page is also the smallestunit that can be selected to a read operation.

Referring to FIGS. 1A-1C, a first exemplary structure according to afirst embodiment of the present disclosure is illustrated. FIG. 1C is amagnified view of an in-process source-level material layers 10′illustrated in FIGS. 1A and 1B. The first exemplary structure includes asemiconductor substrate 8 and semiconductor devices 710 formedthereupon. The semiconductor substrate 8 includes a substratesemiconductor layer 9 at least at an upper portion thereof. Shallowtrench isolation structures 720 can be formed in an upper portion of thesubstrate semiconductor layer 9 to provide electrical isolation fromother semiconductor devices. The semiconductor devices 710 can include,for example, field effect transistors including respective transistoractive regions 742 (i.e., source regions and drain regions), channelregions 746, and gate structures 750. The field effect transistors maybe arranged in a CMOS configuration. Each gate structure 750 caninclude, for example, a gate dielectric 752, a gate electrode 754, adielectric gate spacer 756 and a gate cap dielectric 758. Thesemiconductor devices can include any semiconductor circuitry to supportoperation of a memory structure to be subsequently formed, which istypically referred to as a driver circuitry, which is also known asperipheral circuitry. As used herein, a peripheral circuitry refers toany, each, or all, of word line decoder circuitry, word line switchingcircuitry, bit line decoder circuitry, bit line sensing and/or switchingcircuitry, power supply/distribution circuitry, data buffer and/orlatch, or any other semiconductor circuitry that can be implementedoutside a memory array structure for a memory device. For example, thesemiconductor devices can include word line switching devices forelectrically biasing word lines of three-dimensional memory structuresto be subsequently formed.

Dielectric material layers are formed over the semiconductor devices,which are herein referred to as lower-level dielectric material layers760. The lower-level dielectric material layers 760 can include, forexample, a dielectric liner 762 (such as a silicon nitride liner thatblocks diffusion of mobile ions and/or apply appropriate stress tounderlying structures), first dielectric material layers 764 thatoverlie the dielectric liner 762, a silicon nitride layer (e.g.,hydrogen diffusion barrier) 766 that overlies the first dielectricmaterial layers 764, and at least one second dielectric material layer768.

The dielectric layer stack including the lower-level dielectric materiallayers 760 functions as a matrix for lower-level metal interconnectstructures 780 that provide electrical wiring between the various nodesof the semiconductor devices and landing pads for through-memory-levelcontact via structures to be subsequently formed. The lower-level metalinterconnect structures 780 are formed or included within the dielectriclayer stack of the lower-level dielectric material layers 760, andcomprise a lower-level metal line structure located under and optionallycontacting a bottom surface of the silicon nitride layer 766.

For example, the lower-level metal interconnect structures 780 can beformed within the first dielectric material layers 764. The firstdielectric material layers 764 may be a plurality of dielectric materiallayers in which various elements of the lower-level metal interconnectstructures 780 are sequentially formed. Each dielectric material layerof the first dielectric material layers 764 may include any of dopedsilicate glass, undoped silicate glass, organosilicate glass, siliconnitride, silicon oxynitride, and dielectric metal oxides (such asaluminum oxide). In one embodiment, the first dielectric material layers764 can comprise, or consist essentially of, dielectric material layershaving dielectric constants that do not exceed the dielectric constantof undoped silicate glass (silicon oxide) of 3.9. The lower-level metalinterconnect structures 780 can include various device contact viastructures 782 (e.g., source and drain electrodes which contact therespective source and drain nodes of the device or gate electrodecontacts), intermediate lower-level metal line structures 784,lower-level metal via structures 786, and landing-pad-level metal linestructures 788 that are configured to function as landing pads forthrough-memory-level contact via structures to be subsequently formed.

The landing-pad-level metal line structures 788 can be formed within atopmost dielectric material layer of the first dielectric materiallayers 764 (which can be a plurality of dielectric material layers).Each of the lower-level metal interconnect structures 780 can include ametallic nitride liner and a metal fill structure. Top surfaces of thelanding-pad-level metal line structures 788 and the topmost surface ofthe first dielectric material layers 764 may be planarized by aplanarization process, such as chemical mechanical planarization. Thesilicon nitride layer 766 can be formed directly on the top surfaces ofthe landing-pad-level metal line structures 788 and the topmost surfaceof the first dielectric material layers 764.

The at least one second dielectric material layer 768 may include asingle dielectric material layer or a plurality of dielectric materiallayers. Each dielectric material layer of the at least one seconddielectric material layer 768 may include any of doped silicate glass,undoped silicate glass, and organosilicate glass. In one embodiment, theat least one second dielectric material layer 768 can comprise, orconsist essentially of, dielectric material layers having dielectricconstants that do not exceed the dielectric constant of undoped silicateglass (silicon oxide) of 3.9.

An optional layer of a metallic material and a layer of a semiconductormaterial can be deposited over, or within patterned recesses of, the atleast one second dielectric material layer 768, and is lithographicallypatterned to provide an optional conductive plate layer 6 and in-processsource-level material layers 10′. The optional conductive plate layer 6,if present, provides a high conductivity conduction path for electricalcurrent that flows into, or out of, the in-process source-level materiallayers 10′. The optional conductive plate layer 6 includes a conductivematerial such as a metal or a heavily doped semiconductor material. Theoptional conductive plate layer 6, for example, may include a tungstenlayer having a thickness in a range from 3 nm to 100 nm, although lesserand greater thicknesses can also be used. A metal nitride layer (notshown) may be provided as a diffusion barrier layer on top of theconductive plate layer 6. The conductive plate layer 6 may function as aspecial source line in the completed device. In addition, the conductiveplate layer 6 may comprise an etch stop layer and may comprise anysuitable conductive, semiconductor or insulating layer. The optionalconductive plate layer 6 can include a metallic compound material suchas a conductive metallic nitride (e.g., TiN) and/or a metal (e.g., W).The thickness of the optional conductive plate layer 6 may be in a rangefrom 5 nm to 100 nm, although lesser and greater thicknesses can also beused.

The in-process source-level material layers 10′ can include variouslayers that are subsequently modified to form source-level materiallayers. The source-level material layers, upon formation, include asource semiconductor layer that functions as a common source region forvertical field effect transistors of a three-dimensional memory device.In one embodiment, the in-process source-level material layers 10′ caninclude, from bottom to top, a lower source-level material layer 112, alower sacrificial liner 103, a source-level sacrificial layer 104, anupper sacrificial liner 105, an upper source-level semiconductor layer116, a source-level insulating layer 117, and an optionalsource-select-level conductive layer 118.

The lower source-level material layer 112 and the upper source-levelsemiconductor layer 116 can include a doped semiconductor material suchas doped polysilicon or doped amorphous silicon. The conductivity typeof the lower source-level material layer 112 and the upper source-levelsemiconductor layer 116 can be the opposite of the conductivity ofvertical semiconductor channels to be subsequently formed. For example,if the vertical semiconductor channels to be subsequently formed have adoping of a first conductivity type, the lower source-level materiallayer 112 and the upper source-level semiconductor layer 116 have adoping of a second conductivity type that is the opposite of the firstconductivity type. The thickness of each of the lower source-levelmaterial layer 112 and the upper source-level semiconductor layer 116can be in a range from 10 nm to 300 nm, such as from 20 nm to 150 nm,although lesser and greater thicknesses can also be used.

The source-level sacrificial layer 104 includes a sacrificial materialthat can be removed selective to the lower sacrificial liner 103 and theupper sacrificial liner 105. In one embodiment, the source-levelsacrificial layer 104 can include a semiconductor material such asundoped amorphous silicon or a silicon-germanium alloy with an atomicconcentration of germanium greater than 20%. The thickness of thesource-level sacrificial layer 104 can be in a range from 30 nm to 400nm, such as from 60 nm to 200 nm, although lesser and greaterthicknesses can also be used.

The lower sacrificial liner 103 and the upper sacrificial liner 105include materials that can function as an etch stop material duringremoval of the source-level sacrificial layer 104. For example, thelower sacrificial liner 103 and the upper sacrificial liner 105 caninclude silicon oxide, silicon nitride, and/or a dielectric metal oxide.In one embodiment, each of the lower sacrificial liner 103 and the uppersacrificial liner 105 can include a silicon oxide layer having athickness in a range from 2 nm to 30 nm, although lesser and greaterthicknesses can also be used.

The source-level insulating layer 117 includes a dielectric materialsuch as silicon oxide. The thickness of the source-level insulatinglayer 117 can be in a range from 20 nm to 400 nm, such as from 40 nm to200 nm, although lesser and greater thicknesses can also be used. Theoptional source-select-level conductive layer 118 can include aconductive material that can be used as a source-select-level gateelectrode. For example, the optional source-select-level conductivelayer 118 can include a doped semiconductor material such as dopedpolysilicon or doped amorphous silicon that can be subsequentlyconverted into doped polysilicon by an anneal process. The thickness ofthe optional source-select-level conductive layer 118 can be in a rangefrom 30 nm to 200 nm, such as from 60 nm to 100 nm, although lesser andgreater thicknesses can also be used.

The in-process source-level material layers 10′ can be formed directlyabove a subset of the semiconductor devices on the semiconductorsubstrate 8 (e.g., silicon wafer). As used herein, a first element islocated “directly above” a second element if the first element islocated above a horizontal plane including a topmost surface of thesecond element and an area of the first element and an area of thesecond element has an areal overlap in a plan view (i.e., along avertical plane or direction perpendicular to the top surface of thesemiconductor substrate 8.

The optional conductive plate layer 6 and the in-process source-levelmaterial layers 10′ may be patterned to provide openings in areas inwhich through-memory-level contact via structures and through-dielectriccontact via structures are to be subsequently formed. Patterned portionsof the stack of the conductive plate layer 6 and the in-processsource-level material layers 10′ are present in each memory array region100 in which three-dimensional memory stack structures are to besubsequently formed.

The optional conductive plate layer 6 and the in-process source-levelmaterial layers 10′ can be patterned such that an opening extends over astaircase region 300 in which contact via structures contacting wordline electrically conductive layers are to be subsequently formed. Inone embodiment, the staircase region 300 can be laterally spaced fromthe memory array region 100 along a first horizontal direction hd1. Ahorizontal direction that is perpendicular to the first horizontaldirection hd1 is herein referred to as a second horizontal directionhd2. In one embodiment, additional openings in the optional conductiveplate layer 6 and the in-process source-level material layers 10′ can beformed within the area of a memory array region 100, in which athree-dimensional memory array including memory stack structures is tobe subsequently formed.

The region of the semiconductor devices 710 and the combination of thelower-level dielectric material layers 760 and the lower-level metalinterconnect structures 780 is herein referred to an underlyingperipheral device region 700, which is located underneath a memory-levelassembly to be subsequently formed and includes peripheral devices forthe memory-level assembly. The lower-level metal interconnect structures780 are included in the lower-level dielectric material layers 760.

The lower-level metal interconnect structures 780 can be electricallyconnected to active nodes (e.g., transistor active regions 742 or gateelectrodes 754) of the semiconductor devices 710 (e.g., CMOS devices),and are located at the level of the lower-level dielectric materiallayers 760. Through-memory-level contact via structures can besubsequently formed directly on the lower-level metal interconnectstructures 780 to provide electrical connection to memory devices to besubsequently formed. In one embodiment, the pattern of the lower-levelmetal interconnect structures 780 can be selected such that thelanding-pad-level metal line structures 788 (which are a subset of thelower-level metal interconnect structures 780 located at the topmostportion of the lower-level metal interconnect structures 780) canprovide landing pad structures for the through-memory-level contact viastructures to be subsequently formed.

Referring to FIG. 2, an alternating stack of first material layers andsecond material layers is subsequently formed. Each first material layercan include a first material, and each second material layer can includea second material that is different from the first material. In case atleast another alternating stack of material layer is subsequently formedover the alternating stack of the first material layers and the secondmaterial layers, the alternating stack is herein referred to as afirst-tier alternating stack. The level of the first-tier alternatingstack is herein referred to as a first-tier level, and the level of thealternating stack to be subsequently formed immediately above thefirst-tier level is herein referred to as a second-tier level, etc.

The first-tier alternating stack can include first-tier insulatinglayers 132 as the first material layers, and first spacer materiallayers as the second material layers. In one embodiment, the firstspacer material layers can be sacrificial material layers that aresubsequently replaced with electrically conductive layers. In anotherembodiment, the first spacer material layers can be electricallyconductive layers that are not subsequently replaced with other layers.While the present disclosure is described using embodiments in whichsacrificial material layers are replaced with electrically conductivelayers, embodiments in which the spacer material layers are formed aselectrically conductive layers (thereby obviating the need to performreplacement processes) are expressly contemplated herein.

In one embodiment, the first material layers and the second materiallayers can be first-tier insulating layers 132 and first-tiersacrificial material layers 142, respectively. In one embodiment, eachfirst-tier insulating layer 132 can include a first insulating material,and each first-tier sacrificial material layer 142 can include a firstsacrificial material that is a spacer dielectric material, i.e., adielectric material that vertically spaces the first insulatingmaterial. An alternating plurality of first-tier insulating layers 132and first-tier sacrificial material layers 142 is formed over thein-process source-level material layers 10′. As used herein, a“sacrificial material” refers to a material that is removed during asubsequent processing step.

As used herein, an alternating stack of first elements and secondelements refers to a structure in which instances of the first elementsand instances of the second elements alternate. Each instance of thefirst elements that is not an end element of the alternating pluralityis adjoined by two instances of the second elements on both sides, andeach instance of the second elements that is not an end element of thealternating plurality is adjoined by two instances of the first elementson both ends. The first elements may have the same thicknessthereamongst, or may have different thicknesses. The second elements mayhave the same thickness thereamongst, or may have different thicknesses.The alternating plurality of first material layers and second materiallayers may begin with an instance of the first material layers or withan instance of the second material layers, and may end with an instanceof the first material layers or with an instance of the second materiallayers. In one embodiment, an instance of the first elements and aninstance of the second elements may form a unit that is repeated withperiodicity within the alternating plurality.

The first-tier alternating stack (132, 142) can include first-tierinsulating layers 132 composed of the first material, and first-tiersacrificial material layers 142 composed of the second material, whichis different from the first material. The first material of thefirst-tier insulating layers 132 can be at least one insulatingmaterial. Insulating materials that can be used for the first-tierinsulating layers 132 include, but are not limited to silicon oxide(including doped or undoped silicate glass), silicon nitride, siliconoxynitride, organosilicate glass (OSG), spin-on dielectric materials,dielectric metal oxides that are commonly known as high dielectricconstant (high-k) dielectric oxides (e.g., aluminum oxide, hafniumoxide, etc.) and silicates thereof, dielectric metal oxynitrides andsilicates thereof, and organic insulating materials. In one embodiment,the first material of the first-tier insulating layers 132 can besilicon oxide.

The second material of the first-tier sacrificial material layers 142 isa sacrificial material that can be removed selective to the firstmaterial of the first-tier insulating layers 132. As used herein, aremoval of a first material is “selective to” a second material if theremoval process removes the first material at a rate that is at leasttwice the rate of removal of the second material. The ratio of the rateof removal of the first material to the rate of removal of the secondmaterial is herein referred to as a “selectivity” of the removal processfor the first material with respect to the second material.

The first-tier sacrificial material layers 142 may comprise aninsulating material, a semiconductor material, or a conductive material.The second material of the first-tier sacrificial material layers 142can be subsequently replaced with electrically conductive electrodeswhich can function, for example, as control gate electrodes of avertical NAND device. In one embodiment, the first-tier sacrificialmaterial layers 142 can be material layers that comprise siliconnitride.

In one embodiment, the first-tier insulating layers 132 can includesilicon oxide, and sacrificial material layers can include siliconnitride sacrificial material layers. The first material of thefirst-tier insulating layers 132 can be deposited, for example, bychemical vapor deposition (CVD). For example, if silicon oxide is usedfor the first-tier insulating layers 132, tetraethylorthosilicate (TEOS)can be used as the precursor material for the CVD process. The secondmaterial of the first-tier sacrificial material layers 142 can beformed, for example, CVD or atomic layer deposition (ALD).

The thicknesses of the first-tier insulating layers 132 and thefirst-tier sacrificial material layers 142 can be in a range from 20 nmto 50 nm, although lesser and greater thicknesses can be used for eachfirst-tier insulating layer 132 and for each first-tier sacrificialmaterial layer 142. The number of repetitions of the pairs of afirst-tier insulating layer 132 and a first-tier sacrificial materiallayer 142 can be in a range from 2 to 1,024, and typically from 8 to256, although a greater number of repetitions can also be used. In oneembodiment, each first-tier sacrificial material layer 142 in thefirst-tier alternating stack (132, 142) can have a uniform thicknessthat is substantially invariant within each respective first-tiersacrificial material layer 142.

A first insulating cap layer 170 is subsequently formed over the firstalternating stack (132, 142). The first insulating cap layer 170includes a dielectric material, which can be any dielectric materialthat can be used for the first-tier insulating layers 132. In oneembodiment, the first insulating cap layer 170 includes the samedielectric material as the first-tier insulating layers 132. Thethickness of the first insulating cap layer 170 can be in a range from20 nm to 300 nm, although lesser and greater thicknesses can also beused.

Referring to FIGS. 3A-3C, the first insulating cap layer 170 and thefirst-tier alternating stack (132, 142) can be patterned to form firststepped surfaces in each staircase region 300. The area in which thefirst-tier alternating stack (132, 142) is patterned includes an annulararea that is laterally offset from edges of a semiconductor die. A kerfregion 600 can be provided on the inside of the edges of a semiconductordie. An edge seal region 500 that continuously extends around the entireedge of the semiconductor die can be provided inside the kerf region. Anedge-side staircase region 400 is provided along the inner side of theedge seal region 500. In one embodiment, each staircase region 300 canface the edge-side staircase region 400 around the entire periphery ofthe semiconductor die.

The staircase region 300 can include a respective first stepped area inwhich the first stepped surfaces are formed, and a second stepped areain which additional stepped surfaces are to be subsequently formed in asecond-tier structure (to be subsequently formed over a first-tierstructure) and/or additional tier structures. The first stepped surfacescan be formed, for example, by forming a mask layer with an openingtherein, etching a cavity within the levels of the first insulating caplayer 170, and iteratively expanding the etched area and verticallyrecessing the cavity by etching each pair of a first-tier insulatinglayer 132 and a first-tier sacrificial material layer 142 locateddirectly underneath the bottom surface of the etched cavity within theetched area. In one embodiment, top surfaces of the first-tiersacrificial material layers 142 can be physically exposed at the firststepped surfaces. The cavity overlying the first stepped surfaces isherein referred to as a first stepped cavity.

A dielectric fill material (such as undoped silicate glass or dopedsilicate glass) can be deposited to fill the first stepped cavity.Excess portions of the dielectric fill material can be removed fromabove the horizontal plane including the top surface of the firstinsulating cap layer 170. A remaining portion of the dielectric fillmaterial that fills the region overlying the first stepped surfacesconstitute a first retro-stepped dielectric material portion 165. Asused herein, a “retro-stepped” element refers to an element that hasstepped surfaces and a horizontal cross-sectional area that increasesmonotonically as a function of a vertical distance from a top surface ofa substrate on which the element is present. The first-tier alternatingstack (132, 142) and the first retro-stepped dielectric material portion165 collectively constitute a first-tier structure, which is anin-process structure that is subsequently modified.

An inter-tier dielectric layer 180 may be optionally deposited over thefirst-tier structure (132, 142, 170, 165). The inter-tier dielectriclayer 180 includes a dielectric material such as silicon oxide. In oneembodiment, the inter-tier dielectric layer 180 can include a dopedsilicate glass having a greater etch rate than the material of thefirst-tier insulating layers 132 (which can include an undoped silicateglass). For example, the inter-tier dielectric layer 180 can includephosphosilicate glass. The thickness of the inter-tier dielectric layer180 can be in a range from 30 nm to 300 nm, although lesser and greaterthicknesses can also be used.

Referring to FIGS. 4A and 4B, various first-tier openings (149, 129) canbe formed through the inter-tier dielectric layer 180 and the first-tierstructure (132, 142, 170, 165) and into the in-process source-levelmaterial layers 10′. A photoresist layer (not shown) can be applied overthe inter-tier dielectric layer 180, and can be lithographicallypatterned to form various openings therethrough. The pattern of openingsin the photoresist layer can be transferred through the inter-tierdielectric layer 180 and the first-tier structure (132, 142, 170, 165)and into the in-process source-level material layers 10′ by a firstanisotropic etch process to form the various first-tier openings (149,129) concurrently, i.e., during the first isotropic etch process. Thevarious first-tier openings (149, 129) can include first-tier memoryopenings 149 and first-tier support openings 129. Locations of steps Sin the first alternating stack (132, 142) are illustrated as dottedlines in FIG. 4B.

The first-tier memory openings 149 are openings that are formed in thememory array region 100 through each layer within the first alternatingstack (132, 142) and are subsequently used to form memory stackstructures therein. The first-tier memory openings 149 can be formed inclusters of first-tier memory openings 149 that are laterally spacedapart along the second horizontal direction hd2. Each cluster offirst-tier memory openings 149 can be formed as a two-dimensional arrayof first-tier memory openings 149.

The first-tier support openings 129 are openings that are formed in thestaircase region 300 and are subsequently used to form staircase-regioncontact via structures that interconnect a respective pair of anunderlying lower-level metal interconnect structure 780 (such as alanding-pad-level metal line structure 788) and an electricallyconductive layer (which can be formed as one of the spacer materiallayers or can be formed by replacement of a sacrificial material layerwithin the electrically conductive layer). A subset of the first-tiersupport openings 129 that is formed through the first retro-steppeddielectric material portion 165 can be formed through a respectivehorizontal surface of the first stepped surfaces. Further, each of thefirst-tier support openings 129 can be formed directly above (i.e.,above, and with an areal overlap with) a respective one of thelower-level metal interconnect structure 780.

In one embodiment, the first anisotropic etch process can include aninitial step in which the materials of the first-tier alternating stack(132, 142) are etched concurrently with the material of the firstretro-stepped dielectric material portion 165. The chemistry of theinitial etch step can alternate to optimize etching of the first andsecond materials in the first-tier alternating stack (132, 142) whileproviding a comparable average etch rate to the material of the firstretro-stepped dielectric material portion 165. The first anisotropicetch process can use, for example, a series of reactive ion etchprocesses or a single reaction etch process (e.g., CF₄/O₂/Ar etch). Thesidewalls of the various first-tier openings (149, 129) can besubstantially vertical, or can be tapered.

After etching through the alternating stack (132, 142) and the firstretro-stepped dielectric material portion 165, the chemistry of aterminal portion of the first anisotropic etch process can be selectedto etch through the dielectric material(s) of the at least one seconddielectric material layer 768 with a higher etch rate than an averageetch rate for the in-process source-level material layers 10′. Forexample, the terminal portion of the anisotropic etch process mayinclude a step that etches the dielectric material(s) of the at leastone second dielectric material layer 768 selective to a semiconductormaterial within a component layer in the in-process source-levelmaterial layers 10′. In one embodiment, the terminal portion of thefirst anisotropic etch process can etch through the source-select-levelconductive layer 118, the source-level insulating layer 117, the uppersource-level semiconductor layer 116, the upper sacrificial liner 105,the source-level sacrificial layer 104, and the lower sacrificial liner103, and at least partly into the lower source-level semiconductor layer112. The terminal portion of the first anisotropic etch process caninclude at least one etch chemistry for etching the varioussemiconductor materials of the in-process source-level material layers10′. The photoresist layer can be subsequently removed, for example, byashing.

Optionally, the portions of the first-tier memory openings 149 and thefirst-tier support openings 129 at the level of the inter-tierdielectric layer 180 can be laterally expanded by an isotropic etch. Inthis case, the inter-tier dielectric layer 180 can comprise a dielectricmaterial (such as borosilicate glass) having a greater etch rate thanthe first-tier insulating layers 132 (that can include undoped silicateglass) in dilute hydrofluoric acid. An isotropic etch (such as a wetetch using HF) can be used to expand the lateral dimensions of thefirst-tier memory openings 149 at the level of the inter-tier dielectriclayer 180. The portions of the first-tier memory openings 149 located atthe level of the inter-tier dielectric layer 180 may be optionallywidened to provide a larger landing pad for second-tier memory openingsto be subsequently formed through a second-tier alternating stack (to besubsequently formed prior to formation of the second-tier memoryopenings).

Referring to FIG. 5, sacrificial first-tier opening fill portions (148,128) can be formed in the various first-tier openings (149, 129). Forexample, a sacrificial first-tier fill material is depositedconcurrently deposited in each of the first-tier openings (149, 129).The sacrificial first-tier fill material includes a material that can besubsequently removed selective to the materials of the first-tierinsulating layers 132 and the first-tier sacrificial material layers142.

In one embodiment, the sacrificial first-tier fill material can includea semiconductor material such as silicon (e.g., a-Si or polysilicon), asilicon-germanium alloy, germanium, a III-V compound semiconductormaterial, or a combination thereof. Optionally, a thin etch stop liner(such as a silicon oxide layer or a silicon nitride layer having athickness in a range from 1 nm to 3 nm) may be used prior to depositingthe sacrificial first-tier fill material. The sacrificial first-tierfill material may be formed by a non-conformal deposition or a conformaldeposition method.

In another embodiment, the sacrificial first-tier fill material caninclude a silicon oxide material having a higher etch rate than thematerials of the first-tier insulating layers 132, the first insulatingcap layer 170, and the inter-tier dielectric layer 180. For example, thesacrificial first-tier fill material may include borosilicate glass orporous or non-porous organosilicate glass having an etch rate that is atleast 100 times higher than the etch rate of densified TEOS oxide (i.e.,a silicon oxide material formed by decomposition oftetraethylorthosilicate glass in a chemical vapor deposition process andsubsequently densified in an anneal process) in a 100:1 dilutehydrofluoric acid. In this case, a thin etch stop liner (such as asilicon nitride layer having a thickness in a range from 1 nm to 3 nm)may be used prior to depositing the sacrificial first-tier fillmaterial. The sacrificial first-tier fill material may be formed by anon-conformal deposition or a conformal deposition method.

In yet another embodiment, the sacrificial first-tier fill material caninclude amorphous silicon or a carbon-containing material (such asamorphous carbon or diamond-like carbon) that can be subsequentlyremoved by ashing, or a silicon-based polymer that can be subsequentlyremoved selective to the materials of the first alternating stack (132,142).

Portions of the deposited sacrificial material can be removed from abovethe topmost layer of the first-tier alternating stack (132, 142), suchas from above the inter-tier dielectric layer 180. For example, thesacrificial first-tier fill material can be recessed to a top surface ofthe inter-tier dielectric layer 180 using a planarization process. Theplanarization process can include a recess etch, chemical mechanicalplanarization (CMP), or a combination thereof. The top surface of theinter-tier dielectric layer 180 can be used as an etch stop layer or aplanarization stop layer.

Remaining portions of the sacrificial first-tier fill material comprisesacrificial first-tier opening fill portions (148, 128). Specifically,each remaining portion of the sacrificial material in a first-tiermemory opening 149 constitutes a sacrificial first-tier memory openingfill portion 148. Each remaining portion of the sacrificial material ina first-tier support opening 129 constitutes a sacrificial first-tiersupport opening fill portion 128. The various sacrificial first-tieropening fill portions (148, 128) are concurrently formed, i.e., during asame set of processes including the deposition process that deposits thesacrificial first-tier fill material and the planarization process thatremoves the first-tier deposition process from above the firstalternating stack (132, 142) (such as from above the top surface of theinter-tier dielectric layer 180). The top surfaces of the sacrificialfirst-tier opening fill portions (148, 128) can be coplanar with the topsurface of the inter-tier dielectric layer 180. Each of the sacrificialfirst-tier opening fill portions (148, 128) may, or may not, includecavities therein.

Referring to FIG. 6, a second-tier structure can be formed over thefirst-tier structure (132, 142, 170, 148). The second-tier structure caninclude an additional alternating stack of insulating layers and spacermaterial layers, which can be sacrificial material layers. For example,a second alternating stack (232, 242) of material layers can besubsequently formed on the top surface of the first alternating stack(132, 142). The second alternating stack (232, 242) includes analternating plurality of third material layers and fourth materiallayers. Each third material layer can include a third material, and eachfourth material layer can include a fourth material that is differentfrom the third material. In one embodiment, the third material can bethe same as the first material of the first-tier insulating layer 132,and the fourth material can be the same as the second material of thefirst-tier sacrificial material layers 142.

In one embodiment, the third material layers can be second-tierinsulating layers 232 and the fourth material layers can be secondspacer material layers that provide vertical spacing between eachvertically neighboring pair of the second-tier insulating layers 232. Inone embodiment, the third material layers and the fourth material layerscan be second-tier insulating layers 232 and second-tier sacrificialmaterial layers 242, respectively. The third material of the second-tierinsulating layers 232 may be at least one insulating material. Thefourth material of the second-tier sacrificial material layers 242 maybe a sacrificial material that can be removed selective to the thirdmaterial of the second-tier insulating layers 232. The second-tiersacrificial material layers 242 can include a dielectric spacermaterial, and thus, can be dielectric spacer layers. The second-tiersacrificial material layers 242 may comprise an insulating material, asemiconductor material, or a conductive material. The fourth material ofthe second-tier sacrificial material layers 242 can be subsequentlyreplaced with electrically conductive electrodes which can function, forexample, as control gate electrodes of a vertical NAND device.

In one embodiment, each second-tier insulating layer 232 can include asecond insulating material, and each second-tier sacrificial materiallayer 242 can include a second sacrificial material. In this case, thesecond alternating stack (232, 242) can include an alternating pluralityof second-tier insulating layers 232 and second-tier sacrificialmaterial layers 242. The third material of the second-tier insulatinglayers 232 can be deposited, for example, by chemical vapor deposition(CVD). The fourth material of the second-tier sacrificial materiallayers 242 can be formed, for example, CVD or atomic layer deposition(ALD).

The third material of the second-tier insulating layers 232 can be atleast one insulating material. Insulating materials that can be used forthe second-tier insulating layers 232 can be any material that can beused for the first-tier insulating layers 132. The fourth material ofthe second-tier sacrificial material layers 242 is a sacrificialmaterial that can be removed selective to the third material of thesecond-tier insulating layers 232. Sacrificial materials that can beused for the second-tier sacrificial material layers 242 can be anymaterial that can be used for the first-tier sacrificial material layers142. In one embodiment, the second insulating material can be the sameas the first insulating material, and the second sacrificial materialcan be the same as the first sacrificial material. The first-tiersacrificial material layers 142 and the second-tier sacrificial materiallayers 242 can be first dielectric spacer materials and seconddielectric spacer materials, respectively, that have the same materialcomposition such as the material composition of silicon nitride.

The thicknesses of the second-tier insulating layers 232 and thesecond-tier sacrificial material layers 242 can be in a range from 20 nmto 50 nm, although lesser and greater thicknesses can be used for eachsecond-tier insulating layer 232 and for each second-tier sacrificialmaterial layer 242. The number of repetitions of the pairs of asecond-tier insulating layer 232 and a second-tier sacrificial materiallayer 242 can be in a range from 2 to 1,024, and typically from 8 to256, although a greater number of repetitions can also be used. In oneembodiment, each second-tier sacrificial material layer 242 in thesecond alternating stack (232, 242) can have a uniform thickness that issubstantially invariant within each respective second-tier sacrificialmaterial layer 242.

Second stepped surfaces in the second stepped area can be formed in thestaircase region 300 using a same set of processing steps as theprocessing steps used to form the first stepped surfaces in the firststepped area with suitable adjustment to the pattern of at least onemasking layer. A second retro-stepped dielectric material portion 265can be formed over the second stepped surfaces in the staircase region300.

A second insulating cap layer 270 can be subsequently formed over thesecond alternating stack (232, 242). The second insulating cap layer 270includes a dielectric material that is different from the material ofthe second-tier sacrificial material layers 242. In one embodiment, thesecond insulating cap layer 270 can include silicon oxide. In oneembodiment, the first and second sacrificial material layers (142, 242)can comprise silicon nitride.

Generally speaking, at least one alternating stack of insulating layers(132, 232) and spacer material layers (such as sacrificial materiallayers (142, 242)) can be formed over the in-process source-levelmaterial layers 10′, and at least one retro-stepped dielectric materialportion (165, 265) can be formed over the staircase regions on the atleast one alternating stack (132, 142, 232, 242).

Optionally, drain-select-level isolation structures 72 can be formedthrough a subset of layers in an upper portion of the second-tieralternating stack (232, 242). The second-tier sacrificial materiallayers 242 that are cut by the drain-select-level isolation structures72 correspond to the levels in which drain-select-level electricallyconductive layers are subsequently formed. The drain-select-levelisolation structures 72 include a dielectric material such as siliconoxide. The drain-select-level isolation structures 72 can laterallyextend along a first horizontal direction hd1, and can be laterallyspaced apart along a second horizontal direction hd2 that isperpendicular to the first horizontal direction hd1. The combination ofthe second alternating stack (232, 242), the second retro-steppeddielectric material portion 265, the second insulating cap layer 270,and the optional drain-select-level isolation structures 72 collectivelyconstitute a second-tier structure (232, 242, 265, 270, 72).

At least one inner alternating stack {(132, 142), (232, 242)} can beformed within the areas of the memory array regions 100 and thestaircase regions 300. Each inner alternating stack {(132, 142), (232,242)} can be entirely encircled by the edge-side staircase region 400.An outer alternating stack {(132, 142), (232, 242)} encircles the set ofall memory array regions 100 and all staircase regions 300. The outeralternating stack {(132, 142), (232, 242)} can be laterally spaced fromeach of the at least one inner alternating stack {(132, 142), (232,242)} by a stack a first retro-stepped dielectric material portion 165and a second retro-stepped dielectric material portion 265.

Referring to FIGS. 7A and 7B, various second-tier openings (249, 229)can be formed through the second-tier structure (232, 242, 265, 270,72). A photoresist layer (not shown) can be applied over the secondinsulating cap layer 270, and can be lithographically patterned to formvarious openings therethrough. The pattern of the openings can be thesame as the pattern of the various first-tier openings (149, 129), whichis the same as the sacrificial first-tier opening fill portions (148,128). Thus, the lithographic mask used to pattern the first-tieropenings (149, 129) can be used to pattern the photoresist layer.

The pattern of openings in the photoresist layer can be transferredthrough the second-tier structure (232, 242, 265, 270, 72) by a secondanisotropic etch process to form various second-tier openings (249, 229)concurrently, i.e., during the second anisotropic etch process. Thevarious second-tier openings (249, 229) can include second-tier memoryopenings 249 and second-tier support openings 229.

The second-tier memory openings 249 are formed directly on a top surfaceof a respective one of the sacrificial first-tier memory opening fillportions 148. The second-tier support openings 229 are formed directlyon a top surface of a respective one of the sacrificial first-tiersupport opening fill portions 128. Further, each second-tier supportopenings 229 can be formed through a horizontal surface within thesecond stepped surfaces, which include the interfacial surfaces betweenthe second alternating stack (232, 242) and the second retro-steppeddielectric material portion 265. Locations of steps S in the first-tieralternating stack (132, 142) and the second-tier alternating stack (232,242) are illustrated as dotted lines in FIG. 7B.

The second anisotropic etch process can include an etch step in whichthe materials of the second-tier alternating stack (232, 242) are etchedconcurrently with the material of the second retro-stepped dielectricmaterial portion 265. The chemistry of the etch step can alternate tooptimize etching of the materials in the second-tier alternating stack(232, 242) while providing a comparable average etch rate to thematerial of the second retro-stepped dielectric material portion 265.The second anisotropic etch process can use, for example, a series ofreactive ion etch processes or a single reaction etch process (e.g.,CF₄/O₂/Ar etch). The sidewalls of the various second-tier openings (249,229) can be substantially vertical, or can be tapered. A bottomperiphery of each second-tier opening (249, 229) may be laterallyoffset, and/or may be located entirely within, a periphery of a topsurface of an underlying sacrificial first-tier opening fill portion(148, 128). The photoresist layer can be subsequently removed, forexample, by ashing.

Referring to FIG. 8, the sacrificial first-tier fill material of thesacrificial first-tier opening fill portions (148, 128) can be removedusing an etch process that etches the sacrificial first-tier fillmaterial selective to the materials of the first and second insulatinglayers (132, 232), the first and second sacrificial material layers(142,242), the first and second insulating cap layers (170, 270), andthe inter-tier dielectric layer 180. A memory opening 49, which is alsoreferred to as an inter-tier memory opening 49, is formed in eachcombination of a second-tier memory openings 249 and a volume from whicha sacrificial first-tier memory opening fill portion 148 is removed. Asupport opening 19, which is also referred to as an inter-tier supportopening 19, is formed in each combination of a second-tier supportopenings 229 and a volume from which a sacrificial first-tier supportopening fill portion 128 is removed.

FIGS. 9A-9D provide sequential cross-sectional views of a memory opening49 during formation of a memory opening fill structure. The samestructural change occurs in each of the memory openings 49 and thesupport openings 19.

Referring to FIG. 9A, a memory opening 49 in the first exemplary devicestructure of FIG. 8 is illustrated. The memory opening 49 extendsthrough the first-tier structure and the second-tier structure.

Referring to FIG. 9B, a stack of layers including a blocking dielectriclayer 52, a charge storage layer 54, a tunneling dielectric layer 56,and a semiconductor channel material layer 60L can be sequentiallydeposited in the memory openings 49. The blocking dielectric layer 52can include a single dielectric material layer or a stack of a pluralityof dielectric material layers. In one embodiment, the blockingdielectric layer can include a dielectric metal oxide layer consistingessentially of a dielectric metal oxide. As used herein, a dielectricmetal oxide refers to a dielectric material that includes at least onemetallic element and at least oxygen. The dielectric metal oxide mayconsist essentially of the at least one metallic element and oxygen, ormay consist essentially of the at least one metallic element, oxygen,and at least one non-metallic element such as nitrogen. In oneembodiment, the blocking dielectric layer 52 can include a dielectricmetal oxide having a dielectric constant greater than 7.9, i.e., havinga dielectric constant greater than the dielectric constant of siliconnitride. The thickness of the dielectric metal oxide layer can be in arange from 1 nm to 20 nm, although lesser and greater thicknesses canalso be used. The dielectric metal oxide layer can subsequently functionas a dielectric material portion that blocks leakage of storedelectrical charges to control gate electrodes. In one embodiment, theblocking dielectric layer 52 includes aluminum oxide. Alternatively oradditionally, the blocking dielectric layer 52 can include a dielectricsemiconductor compound such as silicon oxide, silicon oxynitride,silicon nitride, or a combination thereof.

Subsequently, the charge storage layer 54 can be formed. In oneembodiment, the charge storage layer 54 can be a continuous layer orpatterned discrete portions of a charge trapping material including adielectric charge trapping material, which can be, for example, siliconnitride. Alternatively, the charge storage layer 54 can include acontinuous layer or patterned discrete portions of a conductive materialsuch as doped polysilicon or a metallic material that is patterned intomultiple electrically isolated portions (e.g., floating gates), forexample, by being formed within lateral recesses into sacrificialmaterial layers (142, 242). In one embodiment, the charge storage layer54 includes a silicon nitride layer. In one embodiment, the sacrificialmaterial layers (142, 242) and the insulating layers (132, 232) can havevertically coincident sidewalls, and the charge storage layer 54 can beformed as a single continuous layer. Alternatively, the sacrificialmaterial layers (142, 242) can be laterally recessed with respect to thesidewalls of the insulating layers (132, 232), and a combination of adeposition process and an anisotropic etch process can be used to formthe charge storage layer 54 as a plurality of memory material portionsthat are vertically spaced apart. The thickness of the charge storagelayer 54 can be in a range from 2 nm to 20 nm, although lesser andgreater thicknesses can also be used.

The tunneling dielectric layer 56 includes a dielectric material throughwhich charge tunneling can be performed under suitable electrical biasconditions. The charge tunneling may be performed through hot-carrierinjection or by Fowler-Nordheim tunneling induced charge transferdepending on the mode of operation of the monolithic three-dimensionalNAND string memory device to be formed. The tunneling dielectric layer56 can include silicon oxide, silicon nitride, silicon oxynitride,dielectric metal oxides (such as aluminum oxide and hafnium oxide),dielectric metal oxynitride, dielectric metal silicates, alloys thereof,and/or combinations thereof. In one embodiment, the tunneling dielectriclayer 56 can include a stack of a first silicon oxide layer, a siliconoxynitride layer, and a second silicon oxide layer, which is commonlyknown as an ONO stack. In one embodiment, the tunneling dielectric layer56 can include a silicon oxide layer that is substantially free ofcarbon or a silicon oxynitride layer that is substantially free ofcarbon. The thickness of the tunneling dielectric layer 56 can be in arange from 2 nm to 20 nm, although lesser and greater thicknesses canalso be used. The stack of the blocking dielectric layer 52, the chargestorage layer 54, and the tunneling dielectric layer 56 constitutes amemory film 50 that stores memory bits.

The semiconductor channel material layer 60L includes a p-dopedsemiconductor material such as at least one elemental semiconductormaterial, at least one III-V compound semiconductor material, at leastone II-VI compound semiconductor material, at least one organicsemiconductor material, or other semiconductor materials known in theart. In one embodiment, the semiconductor channel material layer 60L canhaving a uniform doping. In one embodiment, the semiconductor channelmaterial layer 60L can include a doped semiconductor material having adoping of a first conductivity type. In another embodiment, thesemiconductor channel material layer 60L can include dopants of thefirst conductivity type at an atomic concentration in a range from1.0×10¹⁴/cm³ to 1.0×10¹⁸/cm³, although lesser and greater dopantsconcentrations can also be used. The semiconductor channel materiallayer 60L can be formed by a conformal deposition method such as lowpressure chemical vapor deposition (LPCVD). The thickness of thesemiconductor channel material layer 60L can be in a range from 2 nm to10 nm, although lesser and greater thicknesses can also be used. Acavity 49′ is formed in the volume of each memory opening 49 that is notfilled with the deposited material layers (52, 54, 56, 60L).

Referring to FIG. 9C, in case the cavity 49′ in each memory opening isnot completely filled by the semiconductor channel material layer 60L, adielectric core layer can be deposited in the cavity 49′ to fill anyremaining portion of the cavity 49′ within each memory opening. Thedielectric core layer includes a dielectric material such as siliconoxide or organosilicate glass. The dielectric core layer can bedeposited by a conformal deposition method such as low pressure chemicalvapor deposition (LPCVD), or by a self-planarizing deposition processsuch as spin coating. The horizontal portion of the dielectric corelayer overlying the second insulating cap layer 270 can be removed, forexample, by a recess etch. The recess etch continues until top surfacesof the remaining portions of the dielectric core layer are recessed to aheight between the top surface of the second insulating cap layer 270and the bottom surface of the second insulating cap layer 270. Eachremaining portion of the dielectric core layer constitutes a dielectriccore 62.

Referring to FIG. 9D, a doped semiconductor material can be deposited incavities overlying the dielectric cores 62. The doped semiconductormaterial has a doping of a second conductivity type that is the oppositeof the first conductivity type. Thus, a p-n junction is formed at eachinterface between the semiconductor channel material layer 60L having adoping of the first conductivity type and the deposited dopedsemiconductor material having a doping of the second conductivity type.Portions of the deposited doped semiconductor material, thesemiconductor channel material layer 60L, the tunneling dielectric layer56, the charge storage layer 54, and the blocking dielectric layer 52that overlie the horizontal plane including the top surface of thesecond insulating cap layer 270 can be removed by a planarizationprocess such as a chemical mechanical planarization (CMP) process.

Each remaining portion of the doped semiconductor material having adoping of the second conductivity type constitutes a drain region 63.The dopant concentration in the drain regions 63 can be in a range from5.0×10¹⁹/cm³ to 2.0×10²¹/cm³, although lesser and greater dopantconcentrations can also be used. The doped semiconductor material canbe, for example, doped polysilicon.

Each remaining portion of the semiconductor channel material layer 60Lconstitutes a vertical semiconductor channel 60 through which electricalcurrent can flow when a vertical NAND device including the verticalsemiconductor channel 60 is turned on. A tunneling dielectric layer 56is surrounded by a charge storage layer 54, and laterally surrounds avertical semiconductor channel 60. Each adjoining set of a blockingdielectric layer 52, a charge storage layer 54, and a tunnelingdielectric layer 56 collectively constitute a memory film 50, which canstore electrical charges with a macroscopic retention time. In someembodiments, a blocking dielectric layer 52 may not be present in thememory film 50 at this step, and a blocking dielectric layer may besubsequently formed after formation of backside recesses. As usedherein, a macroscopic retention time refers to a retention time suitablefor operation of a memory device as a permanent memory device such as aretention time in excess of 24 hours.

Each combination of a memory film 50 and a vertical semiconductorchannel 60 (which is a vertical semiconductor channel) within a memoryopening 49 constitutes a memory stack structure 55. The memory stackstructure 55 is a combination of a vertical semiconductor channel 60, atunneling dielectric layer 56, a plurality of memory elements asembodied as portions of the charge storage layer 54, and an optionalblocking dielectric layer 52. Each combination of a memory stackstructure 55, a dielectric core 62, and a drain region 63 within amemory opening 49 constitutes a memory opening fill structure 58. Thein-process source-level material layers 10′, the first-tier structure(132, 142, 170, 165), the second-tier structure (232, 242, 270, 265,72), the inter-tier dielectric layer 180, and the memory opening fillstructures 58 collectively constitute a memory-level assembly.

Referring to FIGS. 10A-10C, the first exemplary structure is illustratedafter formation of the memory opening fill structures 58. Support pillarstructures 20 are formed in the support openings 19 concurrently withformation of the memory opening fill structures 58. Each support pillarstructure 20 can have a same set of components as a memory opening fillstructure 58. While the present disclosure is described using anembodiment in which the support pillar structures 20 include a same setof structural elements as memory opening fill structures 58, in otherembodiments the support pillar structures 20 are formed at a separateprocessing step than the memory opening fill structures 58. For example,the support openings 19 may be provided as cavities at a differentprocessing step than the processing step at which the memory openings 49are provided as cavities, and a dielectric material such as siliconoxide may be deposited in the support openings 19 to form support pillarstructures that consist of at least one dielectric fill material.

Referring to FIG. 11, a first contact-level dielectric layer 280 and afirst sacrificial semiconductor layer 531 can be sequentially depositedon top of the second insulating cap layer 270. The first contact-leveldielectric layer 280 includes a dielectric material such as siliconoxide, and can be formed by a conformal or non-conformal depositionprocess. For example, the first contact-level dielectric layer 280 caninclude undoped silicate glass and can have a thickness in a range from100 nm to 600 nm, although lesser and greater thicknesses can also beused. The first sacrificial semiconductor layer 531 includes asacrificial semiconductor material such as amorphous silicon,polysilicon, or a silicon-germanium alloy. The thickness of the firstsacrificial semiconductor layer 531 can be in a range from 100 nm to 600nm, although lesser and greater thicknesses can also be used.

A photoresist layer (not shown) can be applied over the firstsacrificial semiconductor layer 531, and can be lithographicallypatterned to form openings in the memory array region 100 and a moatopening that encircles the memory array region 100, the staircaseregions 300, and the edge-side staircase region 400 within the edge sealregion 500. The pattern in the photoresist layer can be transferredthrough the first sacrificial semiconductor layer 531, the firstcontact-level dielectric layer 280, each inner alternating stack {(132,142), (232, 242)} located in the memory array regions 100 and thestaircase regions 300, and the outer alternating stack {(132, 142),(232, 242)} located in the edge seal region 500, the kerf region 600,and the edge-side staircase region 400. Source contact trenches 269extending to a source-level sacrificial layer 104 can be formed througheach inner alternating stack {(132, 142), (232, 242)} within the memoryarray regions 100. A guard ring trench 569 having a shape of a moattrench can be formed through the outer alternating stack {(132, 142),(232, 242)} within the edge seal region 500. In one embodiment, a subsetof the lower-level metal interconnect structures 780 can be configuredto provide a lower-level metallic wall structure in the edge seal regionbetween the top surface of the substrate semiconductor layer 9 and thebottom surface of the silicon nitride layer 766. The lower-levelmetallic wall structure can encircle the entire areas of the memoryarray regions 100 and the staircase regions 300, and can have an annularconfiguration. A continuous top surface of the lower-level metallic wallstructure can be physically exposed at the bottom of the guard ringtrench 569.

Referring to FIG. 12, a dielectric spacer material layer 532L, a secondsacrificial semiconductor layer 534L, and a first sacrificial dielectriclayer 536L can be sequentially deposited. The dielectric spacer materiallayer 532L includes a dielectric material such as silicon oxide, and canbe formed by a conformal deposition process. The thickness of thedielectric spacer material layer 532L is less than one half of the widthof the source contact trenches 269 and is less than one half of thewidth of the guard ring trench 569. In one embodiment, the dielectricspacer material layer 532L can have a thickness in a range from 10 nm to60 nm, although lesser and greater thicknesses can also be used.

The second sacrificial semiconductor layer 534L includes a sacrificialsemiconductor material such as amorphous silicon, polysilicon, or asilicon-germanium alloy. The second sacrificial semiconductor layer 534Lcan fill voids in the source contact trenches 269 and the guard ringtrench 569. The thickness of the second sacrificial semiconductor layer534L can be in a range from 300 nm to 2,000 nm, although lesser andgreater thicknesses can also be used. The first sacrificial dielectriclayer 536L includes a dielectric material such as undoped silicate glassor a doped silicate glass, and can be formed by a conformal ornon-conformal deposition process. For example, the first sacrificialdielectric layer 536L can include undoped silicate glass and can have athickness in a range from 100 nm to 600 nm, although lesser and greaterthicknesses can also be used.

Referring to FIG. 13, a photoresist layer (not shown) can be appliedover the first sacrificial dielectric layer 536L, and can belithographically patterned to form elongated openings in the memoryarray region 100 and at least one moat opening that encircles the guardring trench 569 within the edge seal region 500. The pattern in thephotoresist layer can be transferred through the first sacrificialdielectric layer 536L, the second sacrificial semiconductor layer 534L,the dielectric spacer material layer 532L, the first sacrificialsemiconductor layer 531, the first contact-level dielectric layer 280,each inner alternating stack {(132, 142), (232, 242)} located in thememory array regions 100 and the staircase regions 300, and the outeralternating stack {(132, 142), (232, 242)} located in the edge sealregion 500, the kerf region 600, and the edge-side staircase region 400.

Backside trenches 79 extending to the source-level sacrificial layer 104can be formed through each inner alternating stack {(132, 142), (232,242)} within the memory array regions 100. At least one moat trench,which is herein referred to as at least one crack stopper moat trench579, can be formed through the outer alternating stack {(132, 142),(232, 242)} within the edge seal region 500. Each crack stopper moattrench 579 can be subsequently used to protect the inside of thesemiconductor die from moisture and impurity ingress in case of anycrack in outer portions of the semiconductor die. The at least one crackstopper moat trench 579 can include a plurality of crack stopper moattrenches 579 that encircles the guard ring trench 569.

In one embodiment, an additional subset of the lower-level metalinterconnect structures 780 can be configured to provide at least oneadditional lower-level metallic wall structure in the edge seal regionbetween the top surface of the substrate semiconductor layer 9 and thebottom surface of the silicon nitride layer 766. The at least oneadditional lower-level metallic wall structure can have a respectiveannular configuration, and can encircle the entire areas of thelower-level metallic wall structure that underlies the guard ring trench569. A continuous top surface of a respective additional lower-levelmetallic wall structure can be physically exposed at the bottom of eachcrack stopper moat trenches 579. In one embodiment, the backsidetrenches 79 can laterally extend along the first horizontal directionhd1 (illustrated in FIG. 10B) between neighboring clusters of memoryopening fill structures 58 and midway between a neighboring par ofdrain-select-level isolation structures 72.

Referring to FIG. 14, a conformal spacer material layer can be depositedin the backside trenches 79 and the crack stopper moat trenches 579. Theconformal spacer material layer includes a material that is differentfrom the material of the source-level sacrificial layer 104. Forexample, the conformal spacer material layer can include siliconnitride. An anisotropic etch process is performed to remove horizontalportions of the conformal spacer material layer. Remaining portions ofthe conformal spacer material layer constitute dielectric spacers. Eachremaining vertical portion of the conformal spacer material layer in thebackside trenches 79 constitutes a backside trench spacer 74, and eachremaining vertical portion of the conformal spacer material layer in theat least one crack stopper moat trench 579 constitutes a crack stoppertrench spacer 574. The lateral thickness of each backside trench spacer74 and each crack stopper trench spacer 574 can be in a range from 10 nmto 100 nm, although lesser and greater thicknesses can also be used.Each crack stopper trench spacer 574 comprises an inner dielectricspacer and an outer dielectric spacer that are laterally spaced apart.

Referring to FIG. 15, a sacrificial fill material can be deposited inunfilled volumes of the backside trenches 79 and the at least one crackstopper moat trench 579. Excess portions of the sacrificial fillmaterial can be removed from above the horizontal plane including thetop surface of the first sacrificial dielectric layer 536L by aplanarization process such as a recess etch process and/or a chemicalmechanical planarization process. Each remaining portion of thesacrificial fill material in the backside trenches 79 constitutes asacrificial backside trench fill structure 81, and each remainingportion of the sacrificial fill material in the at least one crackstopper moat trench 579 constitutes a sacrificial moat trench fillstructure 581. The sacrificial backside trench fill structures 81 andthe at least one sacrificial moat trench fill structure 581 can includea sacrificial semiconductor material, which can be, for example,amorphous silicon, polysilicon, or a silicon-germanium alloy.

A second sacrificial dielectric layer 538L can be formed over the firstsacrificial dielectric layer 536L. The second sacrificial dielectriclayer 538L includes a dielectric material such as undoped silicate glassor a doped silicate glass, and can be formed by a conformal ornon-conformal deposition process. For example, the second sacrificialdielectric layer 538L can include undoped silicate glass and can have athickness in a range from 100 nm to 600 nm, although lesser and greaterthicknesses can also be used.

Referring to FIGS. 16 and 17, portions of the second sacrificialdielectric layer 538L can be removed from the memory array regions 100,the staircase regions 300, and the edge-side staircase region 400. Forexample, a photoresist layer (not shown) can be applied over the firstexemplary structure, and can be lithographically patterned to cover theedge seal region 500 and the kerf region 600, and unmasked portions ofthe second sacrificial dielectric layer 538L can be removed by an etchprocess, which may include an isotropic etch process or an anisotropicetch process.

The sacrificial backside trench fill structures 81 can be removedselective to the backside trench spacers 74 and the first sacrificialdielectric layer 536L using a selective etch process. For example, ifthe sacrificial backside trench fill structures 81 include amorphoussilicon, the sacrificial backside trench fill structures 81 can beremoved by a wet etch process using hot trimethyl-2 hydroxyethylammonium hydroxide (“hot TMY”) or tetramethyl ammonium hydroxide (TMAH).A backside cavity 79′ is formed within each volume from which asacrificial backside trench fill structure 81 is removed.

Referring to FIG. 18, an etchant that etches the material of thesource-level sacrificial layer 104 selective to the materials of thefirst alternating stack (132, 142), the second alternating stack (232,242), the first and second insulating cap layers (170, 270), the firstcontact-level dielectric layer 280, the upper sacrificial liner 105, andthe lower sacrificial liner 103 can be introduced into the backsidetrenches in an isotropic etch process. For example, if the source-levelsacrificial layer 104 includes undoped amorphous silicon or an undopedamorphous silicon-germanium alloy, the backside trench spacers 74include silicon nitride, and the upper and lower sacrificial liners(105, 103) include silicon oxide, a wet etch process using hottrimethyl-2 hydroxyethyl ammonium hydroxide (“hot TMY”) or tetramethylammonium hydroxide (TMAH) can be used to remove the source-levelsacrificial layer 104 selective to the backside trench spacers 74 andthe upper and lower sacrificial liners (105, 103). A source cavity 109is formed in the volume from which the source-level sacrificial layer104 is removed.

Wet etch chemicals such as hot TMY and TMAH are selective to dopedsemiconductor materials such as the p-doped semiconductor materialand/or the doped semiconductor materials of the upper source-levelsemiconductor layer 116 and the lower source-level semiconductor layer112. Thus, use of selective wet etch chemicals such as hot TMY and TMAHfor the wet etch process that forms the source cavity 109 provides alarge process window against etch depth variation during formation ofthe backside trenches 79. Specifically, even if sidewalls of the uppersource-level semiconductor layer 116 are physically exposed or even if asurface of the lower source-level semiconductor layer 112 is physicallyexposed upon formation of the source cavity 109 and/or the backsidetrench spacers 74, collateral etching of the upper source-levelsemiconductor layer 116 and/or the lower source-level semiconductorlayer 112 is minimal, and the structural change to the first exemplarystructure caused by accidental physical exposure of the surfaces of theupper source-level semiconductor layer 116 and/or the lower source-levelsemiconductor layer 112 during manufacturing steps do not result indevice failures. Each of the memory opening fill structures 58 isphysically exposed to the source cavity 109. Specifically, each of thememory opening fill structures 58 includes a sidewall and a bottomsurface that are physically exposed to the source cavity 109.

Referring to FIG. 19, a sequence of isotropic etchants, such as wetetchants, can be applied to the physically exposed portions of thememory films 50 to sequentially etch the various component layers of thememory films 50 from outside to inside, and to physically exposecylindrical surfaces of the vertical semiconductor channels 60 at thelevel of the source cavity 109. The upper and lower sacrificial liners(105, 103) can be collaterally etched during removal of the portions ofthe memory films 50 located at the level of the source cavity 109. Thesource cavity 109 can be expanded in volume by removal of the portionsof the memory films 50 at the level of the source cavity 109 and theupper and lower sacrificial liners (105, 103). A top surface of thelower source-level semiconductor layer 112 and a bottom surface of theupper source-level semiconductor layer 116 can be physically exposed tothe source cavity 109. The source cavity 109 is formed by isotropicallyetching the source-level sacrificial layer 104 and a bottom portion ofeach of the memory films 50 selective to at least one source-levelsemiconductor layer (such as the lower source-level semiconductor layer112 and the upper source-level semiconductor layer 116) and the verticalsemiconductor channels 60.

Referring to FIG. 20, a doped semiconductor material having a doping ofthe second conductivity type can be deposited on the physically exposedsemiconductor surfaces around the source cavity 109. The physicallyexposed semiconductor surfaces include bottom portions of outersidewalls of the vertical semiconductor channels 60, a bottom surface ofthe upper source-level semiconductor layer 116, and/or a top surface ofthe lower source-level semiconductor layer 112.

In one embodiment, the doped semiconductor material having a doping ofthe second conductivity type can be deposited on the physically exposedsemiconductor surfaces around the source cavity 109 by a selectivesemiconductor deposition process. A semiconductor precursor gas, anetchant, and a dopant precursor gas can be flowed concurrently into aprocess chamber including the first exemplary structure during theselective semiconductor deposition process. For example, thesemiconductor precursor gas can include silane, disilane, ordichlorosilane, the etchant gas can include gaseous hydrogen chloride,and the dopant precursor gas such as phosphine, arsine, or stibine. Inthis case, the selective semiconductor deposition process grows a dopedsemiconductor material from physically exposed semiconductor surfacesaround the source cavity 109. The deposited doped semiconductor materialforms a source semiconductor layer 114, which can contact sidewalls ofthe vertical semiconductor channels 60 and has a doping of the secondconductivity type. The atomic concentration of the dopants of the secondconductivity type in the deposited semiconductor material can be in arange from 1.0×10²⁰/cm³ to 2.0×10²¹/cm³, such as from 2.0×10²⁰/cm³ to8.0×10²⁰/cm³. The source semiconductor layer 114 as initially formed canconsist essentially of semiconductor atoms and dopant atoms of thesecond conductivity type. Alternatively, at least one non-selectivedoped semiconductor material deposition process can be used to form thesource semiconductor layer 114. Optionally, one or more etch backprocesses may be used in combination with a plurality of selective ornon-selective deposition processes to provide a seamless and/or voidlesssource semiconductor layer 114.

The duration of the selective semiconductor deposition process can beselected such that the source cavity 109 is filled with the sourcesemiconductor layer 114, and the source semiconductor layer 114 contactsbottom end portions of inner sidewalls of the backside trench spacers74. In one embodiment, the source semiconductor layer 114 can be formedby selectively depositing a doped semiconductor material fromsemiconductor surfaces around the source cavity 109. In one embodiment,the doped semiconductor material can include doped polysilicon. Thus,the source-level sacrificial layer 104 can be replaced with the sourcesemiconductor layer 114.

The layer stack including the lower source-level semiconductor layer112, the source semiconductor layer 114, and the upper source-levelsemiconductor layer 116 constitutes a buried source layer (112, 114,116). A p-n junction is present between the source semiconductor layer114 and the upper source-level semiconductor layer 116. The set oflayers including the buried source layer (112, 114, 116), thesource-level insulating layer 117, and the source-select-levelconductive layer 118 constitutes source-level material layers 10, whichreplaces the in-process source-level material layers 10′.

Referring to FIGS. 21A and 21B, the backside trench spacers 74 can beremoved selective to the insulating layers (132, 232), the first andsecond insulating cap layers (170, 270), the first contact-leveldielectric layer 280, and the source semiconductor layer 114 using anisotropic etch process. For example, if the backside trench spacers 74include silicon nitride, a wet etch process using hot phosphoric acidcan be performed to remove the backside trench spacers 74. In oneembodiment, the isotropic etch process that removes the backside trenchspacers 74 can be combined with a subsequent isotropic etch process thatetches the sacrificial material layers (142, 242) selective to theinsulating layers (132, 232), the first and second insulating cap layers(170, 270), the first contact-level dielectric layer 280, and the sourcesemiconductor layer 114.

An oxidation process can be performed to convert physically exposedsurface portions of semiconductor materials into dielectricsemiconductor oxide portions. For example, surfaces portions of thesource semiconductor layer 114 and the upper source-level semiconductorlayer 116 can be converted into dielectric semiconductor oxide plates122, and surface portions of the source-select-level conductive layer118 can be converted into annular dielectric semiconductor oxide spacers124. The dielectric semiconductor oxide plates 122 and the annulardielectric semiconductor oxide spacers 124 are illustrated in FIG. 21B,and are not illustrated in FIG. 21A for clarity.

Referring to FIGS. 22A and 22B, the sacrificial material layers (142,242) are can be removed selective to the insulating layers (132, 232),the first and second insulating cap layers (170, 270), the firstcontact-level dielectric layer 280, and the source semiconductor layer114, the dielectric semiconductor oxide plates 122, and the annulardielectric semiconductor oxide spacers 124. For example, an etchant thatselectively etches the materials of the sacrificial material layers(142, 242) with respect to the materials of the insulating layers (132,232), the first and second insulating cap layers (170, 270), theretro-stepped dielectric material portions (165, 265), and the materialof the outermost layer of the memory films 50 can be introduced into thebackside trenches 79, for example, using an isotropic etch process. Forexample, the sacrificial material layers (142, 242) can include siliconnitride, the materials of the insulating layers (132, 232), the firstand second insulating cap layers (170, 270), the retro-steppeddielectric material portions (165, 265), and the outermost layer of thememory films 50 can include silicon oxide materials.

The isotropic etch process can be a wet etch process using a wet etchsolution, or can be a gas phase (dry) etch process in which the etchantis introduced in a vapor phase into the backside trench 79. For example,if the sacrificial material layers (142, 242) include silicon nitride,the etch process can be a wet etch process in which the first exemplarystructure is immersed within a wet etch tank including phosphoric acid,which etches silicon nitride selective to silicon oxide, silicon, andvarious other materials used in the art.

Backside recesses (143, 243) are formed in volumes from which thesacrificial material layers (142, 242) of each inner alternating stack{(132, 142), (232, 242)} are removed. The backside recesses (143, 243)include first backside recesses 143 that are formed in volumes fromwhich the first-tier sacrificial material layers 142 of each inneralternating stack {(132, 142), (232, 242)} are removed, and secondbackside recesses 243 that are formed in volumes from which thesecond-tier sacrificial material layers 242 of each inner alternatingstack {(132, 142), (232, 242)} are removed. Each of the backsiderecesses (143, 243) can be a laterally extending cavity having a lateraldimension that is greater than the vertical extent of the cavity. Inother words, the lateral dimension of each of the backside recesses(143, 243) can be greater than the height of the respective backsiderecess (143, 243). A plurality of backside recesses (143, 243) can beformed in the volumes from which the material of the sacrificialmaterial layers (142, 242) is removed. Each of the backside recesses(143, 243) can extend substantially parallel to the top surface of thesubstrate semiconductor layer 9. A backside recess (143, 243) can bevertically bounded by a top surface of an underlying insulating layer(132, 232) and a bottom surface of an overlying insulating layer (132,232) within an inner alternating stack {(132, 142), (232, 242)}. In oneembodiment, each of the backside recesses (143, 243) can have a uniformheight throughout. The sacrificial material layers (142, 242) of theouter alternating stack {(132, 142), (232, 242)} are protected by theretro-stepped dielectric material portions (165, 265), and thus, remainintact during formation of the backside recesses (143, 243).

Referring to FIGS. 23A and 23B, a backside blocking dielectric layer(not shown) can be optionally deposited in the backside recesses (143,243) and the backside trenches 79 and over the first contact-leveldielectric layer 280. The backside blocking dielectric layer includes adielectric material such as a dielectric metal oxide, silicon oxide, ora combination thereof. For example, the backside blocking dielectriclayer can include aluminum oxide. The backside blocking dielectric layercan be formed by a conformal deposition process such as atomic layerdeposition or chemical vapor deposition. The thickness of the backsideblocking dielectric layer can be in a range from 1 nm to 20 nm, such asfrom 2 nm to 10 nm, although lesser and greater thicknesses can also beused.

At least one conductive material can be deposited in the plurality ofbackside recesses (243, 243), on the sidewalls of the backside trenches79, and over the first contact-level dielectric layer 280. The at leastone conductive material can be deposited by a conformal depositionmethod, which can be, for example, chemical vapor deposition (CVD),atomic layer deposition (ALD), electroless plating, electroplating, or acombination thereof. The at least one conductive material can include anelemental metal, an intermetallic alloy of at least two elementalmetals, a conductive nitride of at least one elemental metal, aconductive metal oxide, a conductive doped semiconductor material, aconductive metal-semiconductor alloy such as a metal silicide, alloysthereof, and combinations or stacks thereof.

In one embodiment, the at least one conductive material can include atleast one metallic material, i.e., an electrically conductive materialthat includes at least one metallic element. Non-limiting exemplarymetallic materials that can be deposited in the backside recesses (143,243) include tungsten, tungsten nitride, titanium, titanium nitride,tantalum, tantalum nitride, cobalt, and ruthenium. For example, the atleast one conductive material can include a conductive metallic nitrideliner that includes a conductive metallic nitride material such as TiN,TaN, WN, or a combination thereof, and a conductive fill material suchas W, Co, Ru, Mo, Cu, or combinations thereof. In one embodiment, the atleast one conductive material for filling the backside recesses (143,243) can be a combination of titanium nitride layer and a tungsten fillmaterial.

Electrically conductive layers (146, 246) can be formed in the backsiderecesses (143, 243) by deposition of the at least one conductivematerial. A plurality of first electrically conductive layers 146 can beformed in the plurality of first backside recesses 143, a plurality ofsecond electrically conductive layers 246 can be formed in the pluralityof second backside recesses 243, and a continuous metallic materiallayer (not shown) can be formed on the sidewalls of each backside trench79 and over the first contact-level dielectric layer 280. Each of thefirst electrically conductive layers 146 and the second electricallyconductive layers 246 can include a respective conductive metallicnitride liner and a respective conductive fill material. Thus, the firstand second sacrificial material layers (142, 242) can be replaced withthe first and second electrically conductive layers (146, 246),respectively. Specifically, each first-tier sacrificial material layer142 can be replaced with an optional portion of the backside blockingdielectric layer and a first electrically conductive layer 146, and eachsecond-tier sacrificial material layer 242 can be replaced with anoptional portion of the backside blocking dielectric layer and a secondelectrically conductive layer 246. A backside cavity is present in theportion of each backside trench 79 that is not filled with thecontinuous metallic material layer.

Residual conductive material can be removed from inside the backsidetrenches 79. Specifically, the deposited metallic material of thecontinuous metallic material layer can be etched back from the sidewallsof each backside trench 79 and from above the first contact-leveldielectric layer 280, for example, by an anisotropic or isotropic etch.Each remaining portion of the deposited metallic material in the firstbackside recesses constitutes a first electrically conductive layer 146.Each remaining portion of the deposited metallic material in the secondbackside recesses constitutes a second electrically conductive layer246. Sidewalls of the first electrically conductive material layers 146and the second electrically conductive layers can be physically exposedto a respective backside trench 79.

Each electrically conductive layer (146, 246) can be a conductive sheetincluding openings therein. A first subset of the openings through eachelectrically conductive layer (146, 246) can be filled with memoryopening fill structures 58. A second subset of the openings through eachelectrically conductive layer (146, 246) can be filled with the supportpillar structures 20. Each electrically conductive layer (146, 246) canhave a lesser area than any underlying electrically conductive layer(146, 246) because of the first and second stepped surfaces. Eachelectrically conductive layer (146, 246) can have a greater area thanany overlying electrically conductive layer (146, 246) because of thefirst and second stepped surfaces.

In some embodiment, drain-select-level isolation structures 72 may beprovided at topmost levels of the second electrically conductive layers246. A subset of the second electrically conductive layers 246 locatedat the levels of the drain-select-level isolation structures 72constitutes drain select gate electrodes. A subset of the electricallyconductive layer (146, 246) located underneath the drain select gateelectrodes can function as combinations of a control gate and a wordline located at the same level. The control gate electrodes within eachelectrically conductive layer (146, 246) are the control gate electrodesfor a vertical memory device including the memory stack structure 55.

Each of the memory stack structures 55 comprises a vertical stack ofmemory elements located at each level of the electrically conductivelayers (146, 246). A subset of the electrically conductive layers (146,246) can comprise word lines for the memory elements. The semiconductordevices in the underlying peripheral device region 700 can comprise wordline switch devices configured to control a bias voltage to respectiveword lines. The memory-level assembly is located over the substratesemiconductor layer 9. The memory-level assembly includes at least onealternating stack (132, 146, 232, 246) and memory stack structures 55vertically extending through the at least one alternating stack (132,146, 232, 246).

Referring to FIGS. 24A and 24B, a dielectric material can be depositedin the backside trenches 79 and over the first and second sacrificialdielectric layers (536L, 538L). The dielectric material layer caninclude, for example, silicon oxide. A planarization process can beperformed to sequentially remove horizontal portions of the depositeddielectric material overlying the first and second sacrificialdielectric layers (536L, 538L), the first and second sacrificialdielectric layers (536L, 538L), and the horizontal portion of the secondsacrificial semiconductor layer 534L that overlies a horizontal portionof the dielectric spacer material layer 532L. The planarization processcan use at least one chemical mechanical planarization process and/or atleast one recess etch process.

Each remaining portion of the deposited dielectric material that fillsthe backside trenches 79 constitutes a dielectric wall structure 76.Each remaining portion of the second sacrificial semiconductor layer534L located within volumes of the source contact trenches 269 andlaterally surrounded by a respective vertically-extending portion of thedielectric spacer material layer 532L constitutes a sacrificial sourcecontact trench fill structure 234. Each remaining portion of the secondsacrificial semiconductor layer 534L located within volumes of the guardring trench 569 and laterally surrounded by vertically-extendingportions of the dielectric spacer material layer 532L constitutes asacrificial guarding ring fill structure 534. Portions of the crackstopper trench spacers 574 and the sacrificial moat trench fillstructures 581 located above the horizontal plane including the topsurface of the horizontal portion of the dielectric spacer materiallayer 532L can be collaterally removed during the planarization process.

Referring to FIG. 25, the sacrificial source contact trench fillstructures 234, the sacrificial guarding ring fill structure 534, andthe sacrificial moat trench fill structures 581 can be simultaneouslyremoved by an etch process that etches the materials of the sacrificialsource contact trench fill structures 234, the sacrificial guarding ringfill structure 534, and the sacrificial moat trench fill structures 581selective to the material of the dielectric spacer material layer 532Land the crack stopper trench spacers 574. For example, if thesacrificial source contact trench fill structures 234, the sacrificialguarding ring fill structure 534, and the sacrificial moat trench fillstructures 581 include amorphous silicon, the etch process can include awet etch process using hot trimethyl-2 hydroxyethyl ammonium hydroxide(“hot TMY”) or tetramethyl ammonium hydroxide (TMAH). A source contactvia cavity 239 is formed in each volume from which a sacrificial sourcecontact trench fill structure 234 is removed. A guard ring cavity 539 isformed in the volume from which the sacrificial guard ring fillstructure 534 is removed. A moat trench cavity 579′ is formed in eachvolume from which a sacrificial moat trench fill structure 581 isremoved. A top surface of a lower-level metallic wall structure, asembodied as a subset of the lower-level metal interconnect structures780, is physically exposed at the bottom of each moat trench cavity579′.

Referring to FIG. 26, an anisotropic etch process is performed to removehorizontal portions of the dielectric spacer material layer 532L at thebottom of each source contact cavity 239 and at the bottom of the guardring cavity 539. A top surface of a lower-level metallic wall structureis physically exposed at the bottom of the guard ring cavity 539.Horizontal portions of the dielectric spacer material layer 532Loverlying the first sacrificial semiconductor layer 531 can becollaterally removed during the anisotropic etch process. Each remainingvertical portion of the dielectric spacer material layer 532L around arespective source contact cavity 239 constitutes a source dielectricspacer 233. The source semiconductor layer 114 is physically exposed atthe bottom of each source contact cavity 239. Each remaining verticalportion of the dielectric spacer material layer 532L around the guardring cavity 539 constitutes a guard ring dielectric spacer 532. Eachguard ring dielectric spacer 532 comprises an inner dielectric spacerand an outer dielectric spacer that are laterally spaced apart.

An etch process is subsequently performed to remove the firstsacrificial semiconductor layer 531 selective to the materials of thefirst contact-level dielectric layer 280, the source dielectric spacers233, the guard ring dielectric spacer 532, the crack stopper trenchspacers 574, the source semiconductor layer 114, and the lower-levelmetallic wall structure (as embodied as subsets of the lower-level metalinterconnect structures 780).

Referring to FIG. 27, at least one conductive material can besimultaneously deposited in the volumes of the source contact cavities239, the guard ring cavity 539, and the moat trench cavities 579′. Theat least one conductive material can include a metallic liner materialand a metallic fill material. The metallic liner material can include,for example, TiN, TaN, and/or WN. The metallic liner material can beconformally deposited with a thickness in a range from 6 nm to 100 nm,although lesser and greater thicknesses can also be used. The metallicfill material can fill remaining volumes of the source contact cavities239, the guard ring cavity 539, and the moat trench cavities 579′ thatare not filled with the metallic liner material. For example, themetallic fill material can include tungsten, copper, aluminum,ruthenium, cobalt, molybdenum, another elemental metal, an intermetallicalloy thereof, or a combination thereof. Excess portions of the at leastone metallic material can be removed from above the horizontal planeincluding the top surface of the first contact-level dielectric materiallayer 280 by a planarization process, which can use chemical mechanicalplanarization and/or a recess etch.

Each remaining portion of the at least one metallic material in eachsource contact cavity 239 constitutes a source contact via structure238. The remaining portion of the at least one metallic material in theguard ring cavity 539 constitutes a guard ring metallic wall structure548. Each remaining portion of the at least one metallic material in themoat trench cavities 579′ constitutes a crack stop metallic wallstructure 578. Each source contact via structure 238 is formed through afirst alternating stack of insulating layers (132, 232) and electricallyconductive layers (146, 246), which is formed by replacement ofsacrificial material layers (142, 242) in an inner alternating stack{(132, 142), (232, 242)}. The guard ring metallic wall structure 548 andeach crack stop metallic wall structure 578 are formed through the outeralternating stack {(132, 142), (232, 242)}, which is also referred to asa second alternating stack {(132, 142), (232, 242)} henceforth. The atleast one metallic wall structure (548, 578) that includes the guardring metallic wall structure 548 and each crack stop metallic wallstructure 578 is formed vertically through the second alternating stack{(132, 142), (232, 242)}. The at least one metallic wall structure (548,578) divides the second alternating stack {(132, 142), (232, 242)} intomultiple nested portions.

Referring to FIG. 28, a second contact-level dielectric layer 282 may beformed over the first contact-level dielectric layer 280. The secondcontact-level dielectric layer 282 includes a dielectric material suchas silicon oxide, and can have a thickness in a range from 100 nm to 600nm, although lesser and greater thicknesses can also be used.

A photoresist layer (not shown) can be applied over the secondcontact-level dielectric layer 282, and can be lithographicallypatterned to form staircase region openings in the staircase region 300.An anisotropic etch process is performed to transfer the pattern in thephotoresist layer through the second and first contact-level dielectriclayers (282, 280) and underlying dielectric material portions. Theelectrically conductive layers (146, 246) can be used as etch stopstructures. Staircase-region contact via cavities can be formed overeach electrically conductive layer (146, 246) at the stepped surfacesunderlying the first and second retro-stepped dielectric materialportions (165, 265). The photoresist layer can be subsequently removed,for example, by ashing.

Staircase-region contact via structures 86 are formed in thestaircase-region contact via cavities and on a top surface of arespective one of the electrically conductive layers (146, 246). Thestaircase-region contact via structures 86 can include word line contactvia structures that contact electrically conductive layers (146, 246)that function as word lines for the memory stack structures 55. Thestaircase-region contact via structures 86 can further includedrain-select-level contact via structures that contact a subset of thesecond electrically conductive layers 246 that function asdrain-select-level gate electrodes.

Referring to FIG. 29, a third contact-level dielectric layer 284 may beformed over the second contact-level dielectric layer 282. The thirdcontact-level dielectric layer 284 includes a dielectric material suchas silicon oxide, and can have a thickness in a range from 100 nm to 600nm, although lesser and greater thicknesses can also be used.

A photoresist layer (not shown) can be applied over the secondcontact-level dielectric layer 282, and can be lithographicallypatterned to form additional openings in the memory array regions 100,the staircase regions 300, and the edge seal region 500. An anisotropicetch process is performed to transfer the pattern in the photoresistlayer through the third, second, and first contact-level dielectriclayers (284, 282, 280) and underlying dielectric material portions. Thedrain regions 63, the staircase-region contact via structures 86, thesource contact via structures 238, the guard ring metallic wallstructure 548, and the crack stop metallic wall structures 578 can beused as etch stop structures. Various contact via cavities are formedover the drain regions 63, the staircase-region contact via structures86, the source contact via structures 238, the guard ring metallic wallstructure 548, and the crack stop metallic wall structures 578. Thephotoresist layer can be subsequently removed, for example, by ashing.

At least one conductive material can be deposited in the various contactvia cavities, and excess portions of the at least one conductivematerial can be removed from above the horizontal plane including thetop surface of the third contact-level dielectric layer 284. Draincontact via structures 88 are formed on top of the drain regions 63.Staircase-region connection via structures 186 are formed on thestaircase-region contact via structures 86. Source connection viastructures 183 can be formed on the source contact via structures 238. Aguard ring connection via structure 558 is formed on the guard ringmetallic wall structure 548. A crack stop connection via structure 588is formed on each crack stop metallic wall structure 578. The variousvia structures including the drain contact via structures 88, thestaircase-region contact via structures 86, the staircase-regionconnection via structures 186, the source connection via structures 183,the guard ring connection via structure 558, and the crack stopconnection via structures 588 are components of upper-level metalinterconnect structures.

Referring to FIG. 30, additional dielectric layer (herein referred to asupper-level dielectric material layers 960) can be formed over thecontact-level dielectric layers (280, 282, 284), and additionalupper-level metal interconnect structures 980 can be formed in theupper-level dielectric material layers 960. The additional upper-levelmetal interconnect structures 980 can include bit lines 98 contacting arespective one of the drain contact via structures 88, andfirst-line-level metal structures 96 contacting, and/or electricallyconnected to, at least one of the staircase-region connection viastructures 186 and/or source connection via structures 183. Theadditional upper-level metal interconnect structures 980 can furtherinclude various metal via structures and various metal line structuresthat are formed over the bit lines 98 and the first-line-level metalstructures 96 and included in the upper-level dielectric material layers960.

In one embodiment, the three-dimensional memory device comprises amonolithic three-dimensional NAND memory device, the electricallyconductive layers (146, 246) comprise, or are electrically connected to,a respective word line of the monolithic three-dimensional NAND memorydevice, the semiconductor substrate 8 comprises a silicon substrate, themonolithic three-dimensional NAND memory device comprises an array ofmonolithic three-dimensional NAND strings over the silicon substrate,and at least one memory cell in a first device level of the array ofmonolithic three-dimensional NAND strings is located over another memorycell in a second device level of the array of monolithicthree-dimensional NAND strings. The silicon substrate can contain anintegrated circuit comprising a driver circuit for the memory devicelocated thereon, the electrically conductive layers (146, 246) comprisea plurality of control gate electrodes having a strip shape extendingsubstantially parallel to the top surface of the semiconductor substrate8, the plurality of control gate electrodes comprise at least a firstcontrol gate electrode located in the first device level and a secondcontrol gate electrode located in the second device level. The array ofmonolithic three-dimensional NAND strings comprises a plurality ofsemiconductor channels 60, wherein at least one end portion of each ofthe plurality of semiconductor channels 60 extends substantiallyperpendicular to a top surface of the semiconductor substrate 8, and oneof the plurality of semiconductor channels including the verticalsemiconductor channel 60. The array of monolithic three-dimensional NANDstrings comprises a plurality of charge storage elements (as embodied asportions of the memory films 50), each charge storage element locatedadjacent to a respective one of the plurality of semiconductor channels60.

Pad cavities are formed in topmost layer of the upper-level dielectricmaterial layers 960 in the memory array regions 100 and the staircaseregions 300. Moat trenches that encircle the memory array regions 100and the staircase regions 300 are formed in the edge seal region 500.The locations of the moat trenches can be selected such that each moattrench overlies a respective metallic wall structure (548 or 578). Arespective one of the additional upper-level metal interconnectstructures 980 can be exposed at the bottom of each pad cavity. Anannular top surface of an underlying continuous one of the upper-levelmetal interconnect structures 980 can be physically exposed at thebottom of each moat trench.

In one embodiment, the pad cavities can be arranged as a one-dimensionalarray or as a two-dimensional array, and may have a respectivepolygonal, circular, elliptical, or generally-curvilinear shape. Aconductive material can be deposited in the pad cavities and the moattrenches to form various memory-die bonding pads 988 and memory-diebonding strips 988′. The memory-die bonding pads 988 and the memory-diebonding strips 988′ can be formed simultaneously using a same set ofdeposition steps and patterning steps. The memory-die bonding pads 988can include source-network memory-die bonding pads electricallyconnected to the source semiconductor layer 114, word-line-connectionmemory-die bonding pads that are electrically connected to a respectiveone of the electrically conductive layers (146, 246) that function wordlines, and bit-line-connection upper-level memory-die bonding pads thatare electrically connected to the bit lines 98. Each memory-die bondingstrip 988′ can continuously encircle the memory array region 100 and thestaircase region 300, and can overlie a respective one of the metallicwall structures (548 or 578). The first exemplary structure comprises amemory die 900.

The upper-level metal interconnect structures (86, 186, 88, 980, 183,558, 588, 980) include metal via structures and metal line structuresthat are stacked over the guard ring metallic wall structure 548 andeach crack stop metallic wall structure 578 to provide continuous metalbarrier structures that encircle the memory array regions 100 and thestaircase regions 300. At least one vertical stack 940 of metallic sealstructures (780, 548, 578, 588, 980, 988′) is provided in the edge sealregion 500. Each of the at least one vertical stack 940 of metallic sealstructures (780, 548, 578, 588, 980,988′) comprises a respective subset(558, 588, 980) of the upper-level metal interconnect structures (86,186, 88, 980, 183, 558, 588, 980) that contiguously extends between therespective metallic wall structure (548 or 578) and a respectivememory-die bonding strip 988′. Each of the at least one memory-diebonding strip 988′ laterally surrounds, and laterally encloses, thememory-die bonding pads 988. Each of the at least one vertical stack ofmetallic seal structures (780, 548, 578, 588, 980, 988′) comprises arespective memory-die bonding strip 988′.

The collection of all vertical stacks 940 of metallic seal structures(780, 548, 578, 588, 980, 988′) and intervening material portionslocated between neighboring pairs of vertical stacks 940 is hereinreferred to as an edge seal assembly. The edge seal assembly comprisesat least one vertical stack 940 of metallic seal structures (780, 548,578, 588, 980, 988′), which can be a plurality of vertical stacks 940 ofmetallic seal structures (780, 548, 578, 588, 980, 988′). Each of the atleast one vertical stack 940 of metallic seal structures (780, 548, 578,588, 980, 988′) vertically extends contiguously from a top surface ofthe semiconductor substrate 8 to a bonding-side surface of theupper-level dielectric material layers 960, and comprises a respectiveone of the at least one metallic wall structure (548, 578).

In one embodiment, each of the at least one vertical stack 940 ofmetallic seal structures (780, 548, 578, 588, 980, 988′) comprises arespective subset of the lower metal interconnect structures 780 thatcontiguously extends between the respective metallic wall structure (548or 578) and the semiconductor substrate 8. In one embodiment, the atleast one vertical stack 940 of metallic seal structures (780, 548, 578,588, 980, 988′) comprises a plurality of vertical stacks 940 of metallicseal structures (780, 548, 578, 588, 980, 988′). Each of the pluralityof vertical stacks 940 of metallic seal structures (780, 548, 578, 588,980, 988′) laterally surrounds, or is laterally surrounded by, anothervertical stack 940 among the plurality of vertical stacks of metallicseal structures (780, 548, 578, 588, 980, 988′).

Referring to FIG. 31, a support die 800 is provided, which comprisesvarious semiconductor devices 810 formed on a support-die semiconductorlayer 808. The support-die semiconductor layer 808 can include at leastone elemental semiconductor material (e.g., single crystal silicon waferor layer), at least one III-V compound semiconductor material, at leastone II-VI compound semiconductor material, at least one organicsemiconductor material, or other semiconductor materials known in theart.

The semiconductor devices 810 includes peripheral circuitry foroperation of the three-dimensional memory arrays in the memory die 900.The peripheral circuitry can be configured to control operation ofvertical stacks of memory elements in the three-dimensional memory arrayof the memory die 900. For example, the peripheral circuitry can includea word line driver that drives word lines of the three-dimensionalmemory array (as embodied as the electrically conductive layers (146,246)) within the memory die 900, a bit line driver that drives the bitlines 98 in the memory die 900, a word line decoder circuit that decodesthe addresses for the electrically conductive layers (146, 246), a bitline decoder circuit that decodes the addresses for the bit lines 98, asense amplifier circuit that senses the states of memory elements withinthe memory stack structures 55 in the memory die 900, a source powersupply circuit that provides power to source semiconductor layer 114 thememory die 900, a data buffer and/or latch, or any other semiconductorcircuit that can be used to operate the array of memory stack structures55 in the memory die 900.

Shallow trench isolation structures 820 can be provided in a surfaceregion of the support-die semiconductor layer 808 to provide electricalisolation among semiconductor devices of the peripheral circuitry. Thevarious semiconductor devices 810 can include field effect transistors.

Dielectric material layers are formed over the semiconductor devices810, which are herein referred to as support-die dielectric materiallayers 860. Support-die metal interconnect structures 880 are includedwithin the support-die dielectric material layers 860. The support-diemetal interconnect structures 880 can include various device contact viastructures (e.g., source and drain electrodes which contact therespective source and drain nodes of the device or gate electrodecontacts), interconnect-level metal line structures, andinterconnect-level metal via structures. Support-die bonding pads 888and support-die bonding strips 888′ can be formed on the topmost levelof the support-die metal interconnect structures 880. The support-diebonding pads 888 are provided at a bonding-side surface of support-diedielectric material layers 860 that overlie the peripheral circuit. Thesupport-die metal interconnect structures 880 electrically connect nodesof the peripheral circuit to a respective one of the support-die bondingpads 888. The support-die bonding pads 888 can be configured to matewith the memory-die bonding pads 988 of the memory die 900, and thesupport-die bonding strips 888′ can be configured to mate with thememory-die bonding strips 988′.

At least one vertical stack 840 of support-die metallic seal structuresis provided in the support die 800. Each of the at least one verticalstack 840 of support-die metallic seal structures (880, 888′) comprisesa respective subset of the support-die metal interconnect structures 880that contiguously extends between the support-die semiconductor layer808 and a respective support-die bonding strip 888′. Each of the atleast one support-die bonding strip 888′ laterally surrounds, andlaterally encloses, the support-die bonding pads 888. Each of the atleast one vertical stack 840 of support-die metallic seal structures(880, 888′) comprises a respective support-die bonding strip 888′. Inone embodiment, the at least one vertical stack 840 of support-diemetallic seal structures (880, 888′) comprises a plurality of verticalstacks 840 of support-die metallic seal structures (880, 888′). In oneembodiment, the pattern of the at least one vertical stack 840 ofsupport-die metallic seal structures (880, 888′) of the support die 800can be a mirror image of the pattern of the at least one vertical stack940 of metallic seal structures (780, 548, 578, 588, 980, 988′) of thememory die 900.

Referring to FIGS. 32 and 33, the memory die 900 and the support die 800can be bonded to each other using metal-to-metal bonding. Specifically,the memory-die bonding pads 988 can be bonded to the support-die bondingpads 888, and the memory-die bonding strips 988′ can be bonded to thesupport-die bonding strips 888′ by metal-to-metal bonding. Thesupport-die semiconductor layer 808 can be subsequently thinned, forexample, by grinding. The thickness of the support-die semiconductorlayer 808 after grinding can be in a range from 3 microns to 100microns, although lesser and greater thicknesses can also be used.

A backside insulating layer 814 can be deposited on the backside surfaceof the support-die semiconductor layer 808. The backside insulatinglayer 814 can include silicon oxide and/or silicon nitride.Through-substrate via cavities can be formed through the support-diesemiconductor layer 808 and optionally through portion of thesupport-die dielectric material layer 860 on a respective one of thesupport-die metal interconnect structures 880. A through-substrateinsulating spacer 811 and a through-substrate conductive via structure812 can be formed within each through-substrate via cavity. An externalbonding pad 816 can be formed on each of the through-substrateconductive via structures 812.

During bonding of the memory die 900 and the support die 800, eachvertical stack 840 of support-die metallic seal structures (880, 888′)mates with a respective vertical stack 940 of metallic seal structures(780, 548, 578, 588, 980, 988′) to provide an “on-stack” edge sealstructure, which is a continuous metallic seal structure that extendsbetween the semiconductor substrate 8 of the memory die 900 to thesupport-die semiconductor layer 808 of the support die 800. A pluralityof nested continuous metallic seal structures can be provided in thebonded assembly of the memory die 900 and the support die 800. Eachvertical stack 940 of metallic seal structures (780, 548, 578, 588, 980,988′) is formed through the outer alternating stack {(132, 142), (232,242)} of insulating layers (132, 232) and sacrificial material layers(232, 242), and thus, is more resistant to deformation than an edge sealstructure formed within a silicon oxide material portion.

Referring to FIG. 34, a second exemplary structure according to anembodiment of the present disclosure can be derived from the firstexemplary structure by using a vertical stack including a semiconductorsubstrate 8, a dielectric source spacer layer 111, a source-levelsacrificial layer 104, and a source-level insulating layer 117 in lieuof the combination of a semiconductor substrate 8, semiconductor devices710, the lower-level dielectric material layers 760, the lower-levelmetal interconnect structures 780, the optional conductive plate layer6, and the in-process source-level material layers 10′ of the presentdisclosure. The dielectric source spacer layer 111 includes a dielectricmaterial such as silicon oxide, and can have a thickness in a range from50 nm to 500 nm, although lesser and greater thicknesses can also beused. Array region sacrificial etch stop structures 137 may be formed inthe upper portion of the source-level insulating layer 117 in areas inwhich backside trenches are to be subsequently formed. Edge seal regionsacrificial etch stop structures 577 may be formed in the upper portionof the source-level insulating layer 117 in areas in which verticalstacks of metallic seal structures are to be subsequently formed. Eachof the edge seal region sacrificial etch stop structures 577 canlaterally enclose the memory array regions 100 and the staircase regions300, and may be formed as a nested structure.

The processing steps of FIG. 2 through FIGS. 10A-10C can be performed toform at least one inner alternating stack of insulating layers (132,232) and sacrificial material layers (142, 242) in the memory arrayregions 100 and the staircase regions 300, and to form an outeralternating stack of insulating layers (132, 232) and sacrificialmaterial layers (142, 242) in the edge seal region 500, the kerf region600, and the edge-side staircase region 400. In the second exemplarystructure, the memory openings 49 and the memory opening fill structures58 can vertically extend through the source-level sacrificial layer 104and the dielectric source spacer layer 111, and into an upper portion ofthe semiconductor substrate 8. Optionally, formation of the supportpillar structures 20 may be omitted.

Referring to FIG. 35, a first contact-level dielectric layer 280 can bedeposited on top of the second insulating cap layer 270. The firstcontact-level dielectric layer 280 includes a dielectric material suchas silicon oxide, and can be formed by a conformal or non-conformaldeposition process. For example, the first contact-level dielectriclayer 280 can include undoped silicate glass and can have a thickness ina range from 100 nm to 600 nm, although lesser and greater thicknessescan also be used.

A photoresist layer (not shown) can be applied over the firstcontact-level dielectric layer 280, and can be lithographicallypatterned to form openings in the staircase regions 300 and a moatopening that encircles the memory array region 100, the staircaseregions 300, and the edge-side staircase region 400 within the edge sealregion 500. The pattern in the photoresist layer can be transferredthrough the first contact-level dielectric layer 280, each inneralternating stack {(132, 142), (232, 242)} located in the memory arrayregions 100 and the staircase regions 300, and the outer alternatingstack {(132, 142), (232, 242)} located in the edge seal region 500, thekerf region 600, and the edge-side staircase region 400. Supportopenings 319 extending to a top surface of the semiconductor substrate 8can be formed in the staircase regions 300. A guard ring trench 569having a shape of a moat trench can be formed through the outeralternating stack {(132, 142), (232, 242)} within the edge seal region500. In one embodiment, the edge seal region sacrificial etch stopstructures 577 can be located in source-level insulating layer 117within the area of the guard ring trench 569. The edge seal regionsacrificial etch stop structures 577 can have an annular configurationthat encloses the memory array regions 100 and the staircase regions300. A continuous top surface of an edge seal region sacrificial etchstop structure 577 can be physically exposed at the bottom of the guardring trench 569.

Referring to FIG. 36, a dielectric spacer material layer can beconformally deposited in the support openings 319 and the guard ringtrench 569. The dielectric spacer material layer comprises a materialthat is different from the material of the sacrificial material layers(142, 242). For example, the dielectric spacer material layer caninclude silicon oxide. The thickness of the dielectric spacer materiallayer can be greater than one half of the width of each support opening319 and can be less than one half of the width of the guard ring trench569, i.e., less than one half of the lateral separation distance betweena facing pair of an inner sidewall of the guard ring trench 569 and anouter sidewall of the guard ring trench 569.

An anisotropic etch process is performed to remove horizontal portionsof the dielectric spacer material layer from above the firstcontact-level dielectric layer 280 and at the bottom of the guard ringtrench 569. Each support opening 319 is filled with a remaining portionof the dielectric spacer material layer, which constitutes a supportpillar structure 20′ consisting of at least one dielectric material.Remaining vertical portions of the dielectric spacer material layer inthe guard ring trench 569 constitute a guard ring dielectric spacer 532.Each guard ring dielectric spacer 532 comprises an inner dielectricspacer and an outer dielectric spacer that are laterally spaced apart.

Referring to FIG. 37, a sacrificial fill material can be deposited inremaining volumes of the guard ring trench 569 to form a sacrificialguarding ring fill structure 534. The sacrificial guard ring fillstructure 534 can include a semiconductor material such as amorphoussilicon, polysilicon, or a silicon-germanium alloy.

Referring to FIG. 38, a first sacrificial dielectric layer 536L can bedeposited over the first contact-level dielectric layer 280. The firstsacrificial dielectric layer 536L includes a dielectric material such asundoped silicate glass or a doped silicate glass, and can be formed by aconformal or non-conformal deposition process. For example, the firstsacrificial dielectric layer 536L can include undoped silicate glass andcan have a thickness in a range from 100 nm to 600 nm, although lesserand greater thicknesses can also be used.

A photoresist layer (not shown) can be applied over the firstsacrificial dielectric layer 536L, and can be lithographically patternedto form elongated openings in the memory array region 100 and at leastone moat opening that encircles the guard ring trench 569 within theedge seal region 500. The pattern in the photoresist layer can betransferred through the first sacrificial dielectric layer 536L, thefirst contact-level dielectric layer 280, each inner alternating stack{(132, 142), (232, 242)} located in the memory array regions 100 and thestaircase regions 300, and the outer alternating stack {(132, 142),(232, 242)} located in the edge seal region 500, the kerf region 600,and the edge-side staircase region 400.

Backside trenches 79 extending to the array region sacrificial etch stopstructures 137 can be formed through each inner alternating stack {(132,142), (232, 242)} within the memory array regions 100. At least one moattrench, which is herein referred to as at least one crack stopper moattrench 579, can be formed through the outer alternating stack {(132,142), (232, 242)} within the edge seal region 500. Each crack stoppermoat trench 579 can be subsequently used to protect the inside of thesemiconductor die from moisture and impurity ingress in case of anycrack in outer portions of the semiconductor die. The at least one crackstopper moat trench 579 can include a plurality of crack stopper moattrenches 579 that encircles the guard ring trench 569. Each of the atleast one crack stopper moat trench 579 can be formed on a top surfaceof a respective edge seal region sacrificial etch stop structure 577.

Referring to FIG. 39, a temporary fill material that can be subsequentlyremoved selective to the materials of the insulating layers (132, 232)and the sacrificial material layers (142, 242) can be deposited in thebackside trenches 79 and the at least one crack stopper moat trenche579. For example, the temporary fill material can include asemiconductor material such as amorphous silicon, polysilicon, or asilicon-germanium alloy. Excess portions of the temporary fill materialcan be removed from above the first sacrificial dielectric layer 536L.Temporary backside trench fill structures 83 are formed in the backsidetrenches, and temporary moat trench fill structures 583 are formed ineach crack stopper moat trench 579.

Referring to FIG. 40, a second sacrificial dielectric layer 538L can beformed over the first sacrificial dielectric layer 536L. The secondsacrificial dielectric layer 538L includes a dielectric material such asundoped silicate glass or a doped silicate glass, and can be formed by aconformal or non-conformal deposition process. For example, the secondsacrificial dielectric layer 538L can include undoped silicate glass andcan have a thickness in a range from 100 nm to 600 nm, although lesserand greater thicknesses can also be used.

Portions of the second sacrificial dielectric layer 538L can be removedfrom the memory array regions 100, the staircase regions 300, and theedge-side staircase region 400. For example, a photoresist layer (notshown) can be applied over the first exemplary structure, and can belithographically patterned to cover the edge seal region 500 and thekerf region 600, and unmasked portions of the second sacrificialdielectric layer 538L can be removed by an etch process, which mayinclude an isotropic etch process or an anisotropic etch process.

Referring to FIG. 41, the temporary backside trench fill structures 83can be removed selective to the insulating layers (132, 232), thesacrificial material layers (142, 242), and the first sacrificialdielectric layer 536L using a selective etch process. For example, ifthe temporary backside trench fill structures 83 include amorphoussilicon, the sacrificial backside trench fill structures 81 can beremoved by a wet etch process using hot trimethyl-2 hydroxyethylammonium hydroxide (“hot TMY”) or tetramethyl ammonium hydroxide (TMAH).A backside trench 79 including a respective void is provided within eachvolume from which a temporary backside trench fill structure 83 isremoved. Subsequently, the array region sacrificial etch stop structures137 can be subsequently removed. In one embodiment, the temporarybackside trench fill structures 83 and the array region sacrificial etchstop structures 137 include a respective semiconductor material, and thearray region sacrificial etch stop structures 137 can be removedcollaterally during removal of the temporary backside trench fillstructures 83.

Referring to FIG. 42, the processing steps of FIGS. 22A and 22B can beperformed to etch the sacrificial material layers (142, 242) selectiveto the insulating layers (132, 232) of each inner alternating stack{(132, 142), (232, 242)}. Backside recesses (143, 243) are formed involumes from which the sacrificial material layers (142, 242) of eachinner alternating stack {(132, 142), (232, 242)} are removed. Thebackside recesses (143, 243) include first backside recesses 143 thatare formed in volumes from which the first-tier sacrificial materiallayers 142 of each inner alternating stack {(132, 142), (232, 242)} areremoved, and second backside recesses 243 that are formed in volumesfrom which the second-tier sacrificial material layers 242 of each inneralternating stack {(132, 142), (232, 242)} are removed. Each of thebackside recesses (143, 243) can be a laterally extending cavity havinga lateral dimension that is greater than the vertical extent of thecavity. In other words, the lateral dimension of each of the backsiderecesses (143, 243) can be greater than the height of the respectivebackside recess (143, 243). A plurality of backside recesses (143, 243)can be formed in the volumes from which the material of the sacrificialmaterial layers (142, 242) is removed. Each of the backside recesses(143, 243) can extend substantially parallel to the top surface of thesubstrate semiconductor layer 9. A backside recess (143, 243) can bevertically bounded by a top surface of an underlying insulating layer(132, 232) and a bottom surface of an overlying insulating layer (132,232) within an inner alternating stack {(132, 142), (232, 242)}. In oneembodiment, each of the backside recesses (143, 243) can have a uniformheight throughout. The sacrificial material layers (142, 242) of theouter alternating stack {(132, 142), (232, 242)} are protected by theretro-stepped dielectric material portions (165, 265), and thus, remainintact during formation of the backside recesses (143, 243).

Referring to FIG. 43, the processing steps of FIGS. 23A and 23B can beperformed to optionally form a backside blocking dielectric layer (notshown) and electrically conductive layers (146, 246) in each inneralternating stack within the memory array regions 100 and the staircaseregions 300. The electrically conductive layers (146, 246) include firstelectrically conductive layers 146 that are formed within the firstbackside recesses 143 and second electrically conductive layers 246 thatare formed within the second backside recesses 243.

Referring to FIG. 44, an anisotropic etch process can be performed toetch the first sacrificial dielectric layer 536L in the memory arrayregions 100, the staircase regions 300, and the edge-side staircaseregion 400, and to etch the second sacrificial dielectric layer 538L inthe edge seal region 500 and the kerf region 600. In one embodiment, thesecond sacrificial dielectric layer 538L can have about the samethickness as the first sacrificial dielectric layer 536L, and the firstsacrificial dielectric layer 536L can be completely removed in thememory array regions 100, the staircase regions 300, and the edge-sidestaircase region 400, while the first sacrificial dielectric layer 536Lremains in the edge seal region 500 and the kerf region 600. Topsurfaces of the temporary moat trench fill structures 583 can bephysically exposed in the edge seal region 500.

An etch process that etches the material of the temporary moat trenchfill structures 583 selective to the materials of the insulating layers(132, 232), the sacrificial material layers (142, 242), and theelectrically conductive layers (146, 246) can be performed. For example,if the temporary moat trench fill structures 583 include amorphoussilicon, a wet etch process using hot trimethyl-2 hydroxyethyl ammoniumhydroxide (“hot TMY”) or tetramethyl ammonium hydroxide (TMAH) can beperformed to remove the temporary moat trench fill structures 583. Theedge seal region sacrificial etch stop structures 577 can besubsequently removed. In one embodiment, the edge seal regionsacrificial etch stop structures 577 include a semiconductor materialsuch as amorphous silicon, and is collaterally removed during removal ofthe temporary moat trench fill structures 583. A crack stopper moattrench 579 is provided within each volume from which a temporary moattrench fill structure 583 and an underlying edge seal region sacrificialetch stop structure 577 is removed.

Referring to FIG. 45, a conformal spacer material layer can be depositedin the backside trenches 79 and the crack stopper moat trenches 579. Theconformal spacer material layer includes a material that is differentfrom the material of the source-level sacrificial layer 104. Forexample, the conformal spacer material layer can include siliconnitride. An anisotropic etch process is performed to remove horizontalportions of the conformal spacer material layer. Remaining portions ofthe conformal spacer material layer constitute dielectric spacers. Eachremaining vertical portion of the conformal spacer material layer in thebackside trenches 79 constitutes a backside trench spacer 74, and eachremaining vertical portion of the conformal spacer material layer in theat least one crack stopper moat trench 579 constitutes a crack stoppertrench spacer 574. The lateral thickness of each backside trench spacer74 and each crack stopper trench spacer 574 can be in a range from 10 nmto 100 nm, although lesser and greater thicknesses can also be used.Each crack stopper trench spacer 574 comprises an inner dielectricspacer and an outer dielectric spacer that are laterally spaced apart.The anisotropic etch process can be continued until each backside cavity79′ located inside the backside trench spacers 74 vertically extend to atop surface of the source-level sacrificial layer 104 and each moattrench cavity 579′ located inside the crack stopper trench spacers 574vertically extend to a top surface of the semiconductor substrate 8.

Referring to FIG. 46, a sacrificial fill material can be deposited inthe backside cavities 79′ and each moat trench cavity 579′. Excessportions of the sacrificial fill material can be removed from above thefirst contact-level dielectric layer 280 or from above the firstsacrificial dielectric layer 536L by a planarization process such as arecess etch process. Each remaining portion of the sacrificial fillmaterial in the backside cavities 79′ constitutes a sacrificial backsidetrench fill structure 81, and each remaining portion of the sacrificialfill material in the at least one moat trench cavity 579′ constitutes asacrificial moat trench fill structure 581. The sacrificial backsidetrench fill structures 81 and the at least one sacrificial moat trenchfill structure 581 can include a sacrificial semiconductor material,which can be, for example, amorphous silicon, polysilicon, or asilicon-germanium alloy.

Referring to FIG. 47, a sacrificial dielectric cover layer 564 can beformed over the at least one sacrificial moat trench fill structure 581in the edge seal region 500. For example, a dielectric material such asa silicon oxide layer can be deposited over the at least one sacrificialmoat trench fill structure 581, and can be subsequently patterned, forexample, by etching the portion of the deposited dielectric materialfrom the areas of the memory array regions 100, the staircase regions300, and the edge-side staircase region 400.

Subsequently, an isotopic etch process can be performed to remove thesacrificial backside trench fill structures 81 and the source-levelsacrificial layer 104. For example, the sacrificial backside trench fillstructures 81 and the source-level sacrificial layer 104 can include asemiconductor material such as amorphous silicon, and a wet etch processusing hot trimethyl-2 hydroxyethyl ammonium hydroxide (“hot TMY”) ortetramethyl ammonium hydroxide (TMAH) can be performed to remove thesacrificial backside trench fill structures 81 and the source-levelsacrificial layer 104. Backside cavities 79′ are formed in volumes fromwhich the sacrificial backside trench fill structures 81 are removed. Asource cavity 109 can be formed in the volume from which thesource-level sacrificial layer 104 is removed. Subsequently, theprocessing steps of FIG. 19 can be performed to remove cylindricalportions of the memory films 50 at the level of the source cavity 109and to physically expose cylindrical outer surfaces of the verticalsemiconductor channels 60 of the memory opening fill structures 58around the source cavity 109.

Referring to FIG. 48, a non-selective semiconductor deposition processcan be performed to conformally deposit a doped semiconductor materiallayer having a doping of the second conductivity type. Dopants of thesecond conductivity type can be introduced into the depositedsemiconductor material by in-situ doping. Atomic concentration ofdopants of the second conductivity type can be in a range from5.0×10¹⁹/cm³ to 2.0×10²¹/cm³, although lesser and greater atomicconcentrations can also be used. form a source semiconductor layer 114.The portion of the doped semiconductor material that fills the sourcecavity 109 constitutes a source semiconductor layer 114. A dopedsemiconductor material layer 175L is present within the backsidecavities 79′ and over the first contact-level dielectric layer 280.

Referring to FIG. 49, portions of the doped semiconductor material layer175L, the sacrificial dielectric cover layer 564, and the firstsacrificial dielectric layer 536L can be removed from the edge sealregion 500 and the kerf region 600, for example, by covering the memoryarray regions 100, the staircase regions 300, and the edge-sidestaircase region 400 with a patterned photoresist layer (not shown), andby isotropically or anisotropically etching the materials of the dopedsemiconductor material layer 175L, the sacrificial dielectric coverlayer 564, and the first sacrificial dielectric layer 536L. Thepatterned photoresist layer can be removed, for example, by ashing.

Referring to FIG. 50, the sacrificial moat trench fill structures 581can be removed selective to the crack stopper trench spacers 574. Forexample, if the sacrificial moat trench fill structures 581 includeundoped amorphous silicon, the sacrificial moat trench fill structures581 can be removed selective to the doped semiconductor material layer175L by a wet etch process using hot trimethyl-2 hydroxyethyl ammoniumhydroxide (“hot TMY”) or tetramethyl ammonium hydroxide (TMAH). Undopedamorphous silicon can be etched at a significantly high etch rate thanundoped amorphous silicon in such wet etch processes. A moat trenchcavity 579′ is provided in each volume from which a sacrificial moattrench fill structure 581 is removed.

Referring to FIG. 51, the doped semiconductor material of the dopedsemiconductor material layer 175L can be etched from above the topsurface of the first contact-level dielectric layer 280 and from anupper portion of the backside cavities 79′. Each remaining portion ofthe doped semiconductor material of the doped semiconductor materiallayer 175L located at a lower portion of a respective backside trench 79is herein referred to as a lower source contact portion 175. An upperportion of each trench cavity 79′ can be void, and is herein referred toas an upper backside cavity 179′.

Referring to FIG. 52, at least one conductive material can besimultaneously deposited in the volumes of the upper backside cavity179′ and the moat trench cavities 579′ by performing the processingsteps of FIG. 27. The at least one conductive material can include ametallic liner material and a metallic fill material. The metallic linermaterial can include, for example, TiN, TaN, and/or WN. The metallicliner material can be conformally deposited with a thickness in a rangefrom 6 nm to 100 nm, although lesser and greater thicknesses can also beused. The metallic fill material can fill remaining volumes of the upperbackside cavity 179′ and the moat trench cavities 579′ that are notfilled with the metallic liner material. For example, the metallic fillmaterial can include tungsten, copper, aluminum, ruthenium, cobalt,molybdenum, another elemental metal, an intermetallic alloy thereof, ora combination thereof. Excess portions of the at least one metallicmaterial can be removed from above the horizontal plane including thetop surface of the first contact-level dielectric material layer 280 bya planarization process, which can use chemical mechanical planarizationand/or a recess etch.

Each remaining portion of the at least one metallic material in eachupper backside cavity 179′ constitutes an upper source contact portion176. Each contiguous stack of a lower source contact portion 175 and anupper source contact portion 176 constitutes a source contact viastructure (175, 176). Each remaining portion of the at least onemetallic material in the guard ring cavity 539 constitutes a guard ringmetallic wall structure 548. Each remaining portion of the at least onemetallic material in a crack stopper moat trench 579 constitutes a crackstop metallic wall structure 578. Each source contact via structure(175, 176) is formed through a first alternating stack of insulatinglayers (132, 232) and electrically conductive layers (146, 246), whichis formed by replacement of sacrificial material layers (142, 242) in aninner alternating stack {(132, 142), (232, 242)}. The guard ringmetallic wall structure 548 and each crack stop metallic wall structure578 are formed through the outer alternating stack {(132, 142), (232,242)}, which is also referred to as a second alternating stack {(132,142), (232, 242)} henceforth. The at least one metallic wall structure(548, 578) that includes the guard ring metallic wall structure 548 andeach crack stop metallic wall structure 578 is formed vertically throughthe second alternating stack {(132, 142), (232, 242)}. The at least onemetallic wall structure (548, 578) divides the second alternating stack{(132, 142), (232, 242)} into multiple nested portions.

Referring to FIG. 53, the processing steps of FIG. 28 can be performedto form a second contact-level dielectric layer 282 and staircase-regioncontact via structures 86.

Referring to FIG. 54, the processing steps of FIG. 29 can be performedto form a third contact-level dielectric layer 284 and variousconductive via structures, which can include, for example, drain contactvia structures 88, the staircase-region connection via structures 186,the source connection via structures 183, the guard ring connection viastructure 558, and the crack stop connection via structures 588.

Subsequently, the processing steps of FIG. 30 can be performed toprovide a memory die including continuous metal barrier structures thatencircle the memory array regions 100 and the staircase regions 300.Referring to FIGS. 30 and 54 collectively, one of the differencesbetween the first exemplary structure and the second exemplary structureis that each metallic wall structure (548, 578) directly contacts thesemiconductor substrate 8. At least one vertical stack 940 of metallicseal structures (548, 578, 588, 980, 988′) is provided in the edge sealregion 500. Each of the at least one vertical stack 940 of metallic sealstructures (548, 578, 588, 980,988′) comprises a respective subset (558,588, 980) of the upper-level metal interconnect structures (86, 186, 88,980, 183, 558, 588, 980) that contiguously extends between therespective metallic wall structure (548 or 578) and a respectivememory-die bonding strip 988′. Each of the at least one memory-diebonding strip 988′ laterally surrounds, and laterally encloses, thememory-die bonding pads 988. Each of the at least one vertical stack ofmetallic seal structures (548, 578, 588, 980, 988′) comprises arespective memory-die bonding strip 988′.

The collection of all vertical stack 940 of metallic seal structures(548, 578, 588, 980, 988′) and intervening material portions locatedbetween neighboring pairs of vertical stacks 940 is herein referred toas an edge seal assembly. The edge seal assembly comprises at least onevertical stack 940 of metallic seal structures (548, 578, 588, 980,988′), which can be a plurality of vertical stacks 940 of metallic sealstructures (548, 578, 588, 980, 988′). Each of the at least one verticalstack 940 of metallic seal structures (548, 578, 588, 980, 988′)vertically extends contiguously from a top surface of the semiconductorsubstrate 8 to a bonding-side surface of the upper-level dielectricmaterial layers 960, and comprises a respective one of the at least onemetallic wall structure (548, 578).

In one embodiment, each of the at least one vertical stack 940 ofmetallic seal structures (548, 578, 588, 980, 988′) comprises arespective subset of the lower metal interconnect structures 780 thatcontiguously extends between the respective metallic wall structure (548or 578) and the semiconductor substrate 8. In one embodiment, the atleast one vertical stack 940 of metallic seal structures (548, 578, 588,980, 988′) comprises a plurality of vertical stacks 940 of metallic sealstructures (548, 578, 588, 980, 988′). Each of the plurality of verticalstacks 940 of metallic seal structures (548, 578, 588, 980, 988′)laterally surrounds, or is laterally surrounded by, another verticalstack 940 among the plurality of vertical stacks of metallic sealstructures (548, 578, 588, 980, 988′).

Subsequently, the processing steps of FIG. 31 can be performed toprovide a support die 800. The support die 800 can be bonded to thememory die 900 derived from the second exemplary structure by performingthe processing steps of FIG. 32.

Referring to all drawings and according to various embodiments of thepresent disclosure, a three-dimensional memory device comprising amemory die 900 is provided, wherein the memory die 900 comprises: afirst alternating stack (such as an inner alternating stack located in amemory array region 100 and a staircase region 300) of first insulatinglayers (132, 232) and electrically conductive layers (146, 246) locatedover a semiconductor substrate 8; memory stack structures 55 verticallyextending through the first alternating stack {(132, 246), (232, 246)}and comprising vertical stacks of memory elements; a second alternatingstack (such as an outer alternating stack located in the edge sealregion 500) of second insulating layers (132, 232) and spacer dielectriclayers (142, 242) that laterally surrounds the first alternating stack{(132, 246), (232, 246)} and is located over the semiconductor substrate8; memory-die bonding pads 988 included in upper-level dielectricmaterial layers 960 and located on a bonding-side surface of the memorydie 900; and an edge seal assembly comprising at least one verticalstack 940 of metallic seal structures (780 if present, 548, 578, 588,980, 988′), wherein each of the at least one vertical stack 940 ofmetallic seal structures (780 if present, 548, 578, 588, 980, 988′)vertically extends contiguously from a top surface of the semiconductorsubstrate 8 to the bonding-side surface of the memory die 900 andcomprises a respective metallic wall structure (548 or 578) that extendsthrough the second alternating stack {(132, 242), (232, 242)} andlaterally encloses the first alternating stack {(132, 142), (232, 242)},wherein the second alternating stack {(132, 142), (232, 242)} comprisesmultiple nested portions divided by the respective metallic wallstructure (548 or 578).

In one embodiment, each of the at least one vertical stack 940 ofmetallic seal structures (780 if present, 548, 578, 588, 980, 988′)comprises a respective memory-die bonding strip 988′ located at thebonding-side surface and laterally surrounds each of the memory-diebonding pads 988.

In one embodiment, the at least one vertical stack 940 of metallic sealstructures (780 if present, 548, 578, 588, 980, 988′) comprises aplurality of vertical stacks 940 of metallic seal structures (780 ifpresent, 548, 578, 588, 980, 988′); and each of the plurality ofvertical stacks 940 of metallic seal structures (780 if present, 548,578, 588, 980, 988′) laterally surrounds, or is laterally surrounded by,another vertical stack 940 among the plurality of vertical stacks ofmetallic seal structures (780 if present, 548, 578, 588, 980, 988′).

In one embodiment, each of the at least one vertical stack 940 ofmetallic seal structures (780 if present, 548, 578, 588, 980, 988′)comprises a respective set of at least one upper-level metalinterconnect structure (588, 980) that contiguously extends between therespective metallic wall structure (548 or 578) and the respectivememory-die bonding pad 988.

In one embodiment, the memory die 900 comprises at least one dielectricmaterial layer (such as lower-level dielectric material layers 760)located between the semiconductor substrate 8 and the second alternatingstack {(132, 242), (232, 242)}; and each of the at least one verticalstack 940 of metallic seal structures (780, 548, 578, 588, 980, 988′)comprises a respective set of at least one lower metal interconnectstructure 780 that contiguously extends between the respective metallicwall structure (548 or 578) and the semiconductor substrate 8 throughthe at least one dielectric material layer (such as lower-leveldielectric material layers 760).

In one embodiment, each metallic wall structure (548 or 578) directlycontacts a surface of the semiconductor substrate 8.

In one embodiment, each metallic wall structure (548 or 578) within theat least one vertical stack 940 contacts, and laterally surrounds, arespective inner dielectric spacer (an inner dielectric spacer of aguard ring dielectric spacer 532 or a crack stopper trench spacer 574),and contacts, and is laterally surrounded by, a respective outerdielectric spacer (an outer dielectric spacer of a guard ring dielectricspacer 532 or a crack stopper trench spacer 574) having a samecomposition and a same thickness as the respective inner dielectricspacer.

In one embodiment, each of the memory stack structures 55 comprises amemory film 50 and a vertical semiconductor channel 60, the memory film50 including a respective vertical stack of memory elements; and eachmetallic wall structure (548 or 578) within the at least one verticalstack 940 protrudes above a horizontal plane including top surfaces ofthe memory stack structures 55 (such as the horizontal plane includingthe bottom surface of the first contact-level dielectric layer 280).

In one embodiment, the first alternating stack {(132, 146), (232, 246)}comprises a first staircase region (such as a portion located inside thearea of a staircase region 300) in which a lateral extent of layerswithin the first alternating stack {(132, 146), (232, 246)} decreasesstepwise with an increase in a vertical distance from the semiconductorsubstrate 8; and the second alternating stack {(132, 142), (232, 242)}comprises a second staircase region (such as a portion located insidethe area of the edge-side staircase region 400) in which a lateralextent of layers within the second alternating stack {(132, 142), (232,242)} decreases stepwise with an increase in the vertical distance fromthe semiconductor substrate 8.

In one embodiment, the memory die 900 comprises a retro-steppeddielectric material portion (165 and/or 265) that laterally encloses,and contacts, the first alternating stack {(132, 146), (232, 246)} andis laterally enclosed by, and contacts, the second alternating stack{(132, 142), (232, 242)}.

In one embodiment, the memory die 900 has a rectangular horizontalcross-sectional shape bounded by four straight sidewalls; and eachrespective metallic wall structure (548 or 578) comprises four metallicwall segments that are parallel to a respective one of the four straightsidewalls.

In one embodiment, a total number of the first insulating layers (132,232) in the first alternating stack {(132, 146), (232, 246)} is the sameas a total number of the second insulating layers (132, 232) in thesecond alternating stack {(132, 142), (232, 242)}; and each firstinsulating layer in the first alternating stack {(132, 146), (232, 246)}is vertically spaced from the semiconductor substrate 8 by a samevertical distance as a respective one of the second insulating layers(132, 232) in the second alternating stack {(132, 142), (232, 242)} isfrom the semiconductor substrate 8.

In one embodiment, the first insulating layers (132, 232) and the secondinsulating layers (132, 232) comprise silicon oxide; the electricallyconductive layers (146, 246) comprise at least one metallic material;and the spacer dielectric layers (142, 242) comprise silicon nitride.

In one embodiment, the three-dimensional memory device further comprisesa support die 800 bonded to the memory die 900, wherein the support die800 comprises: a peripheral circuit configured to control operation ofthe vertical stacks of memory elements; support-die bonding pads 888that are bonded to the memory-die bonding pads 988; and support-diemetal interconnect structures 880 electrically connecting nodes of theperipheral circuit to a respective one of the support-die bonding pads888 and included in support-die dielectric material layers 860.

The various embodiments of the present disclosure provide deformationresistance to the vertical stack 940 of metallic seal structures (780,548, 578, 588, 980, 988′) by forming the vertical stacks 940 in thesecond alternating stack (such as an outer alternating stack located inthe edge seal region 500) of second insulating layers (132, 232) andspacer dielectric layers (142, 242), which is more deformation resistantthan a continuous silicon oxide portion.

Although the foregoing refers to particular embodiments, it will beunderstood that the disclosure is not so limited. It will occur to thoseof ordinary skill in the art that various modifications may be made tothe disclosed embodiments and that such modifications are intended to bewithin the scope of the disclosure. Compatibility is presumed among allembodiments that are not alternatives of one another. The word“comprise” or “include” contemplates all embodiments in which the word“consist essentially of” or the word “consists of” replaces the word“comprise” or “include,” unless explicitly stated otherwise. Where anembodiment using a particular structure and/or configuration isillustrated in the present disclosure, it is understood that the presentdisclosure may be practiced with any other compatible structures and/orconfigurations that are functionally equivalent provided that suchsubstitutions are not explicitly forbidden or otherwise known to beimpossible to one of ordinary skill in the art. All of the publications,patent applications and patents cited herein are incorporated herein byreference in their entirety.

What is claimed is:
 1. A three-dimensional memory device comprising amemory die, wherein the memory die comprises: a first alternating stackof first insulating layers and electrically conductive layers locatedover a semiconductor substrate; memory stack structures verticallyextending through the first alternating stack and comprising verticalstacks of memory elements; a second alternating stack of secondinsulating layers and spacer dielectric layers that laterally surroundsthe first alternating stack and is located over the semiconductorsubstrate; memory-die bonding pads included in upper-level dielectricmaterial layers and located on a bonding-side surface of the memory die;and an edge seal assembly comprising at least one vertical stack ofmetallic seal structures, wherein each of the at least one verticalstack of metallic seal structures vertically extends from a top surfaceof the semiconductor substrate to the bonding-side surface of the memorydie and comprises a respective metallic wall structure that extendsthrough the second alternating stack and laterally encloses the firstalternating stack.
 2. The three-dimensional memory device of claim 1,wherein each of the at least one vertical stack of metallic sealstructures comprises a respective memory-die bonding strip located atthe bonding-side surface and that laterally surrounds each of thememory-die bonding pads.
 3. The three-dimensional memory device of claim2, wherein: the at least one vertical stack of metallic seal structurescomprises a plurality of vertical stacks of metallic seal structures;and each of the plurality of vertical stacks of metallic seal structureslaterally surrounds, or is laterally surrounded by, another verticalstack among the plurality of vertical stacks of metallic sealstructures.
 4. The three-dimensional memory device of claim 2, whereineach of the at least one vertical stack of metallic seal structurescomprises a respective set of at least one upper-level metalinterconnect structure that extends between the respective metallic wallstructure and the respective memory-die bonding pad.
 5. Thethree-dimensional memory device of claim 4, wherein: the memory diecomprises at least one dielectric material layer located between thesemiconductor substrate and the second alternating stack; and each ofthe at least one vertical stack of metallic seal structures comprises arespective set of at least one lower metal interconnect structure thatextends between the respective metallic wall structure and thesemiconductor substrate through the at least one dielectric materiallayer.
 6. The three-dimensional memory device of claim 4, wherein eachmetallic wall structure directly contacts a surface of the semiconductorsubstrate.
 7. The three-dimensional memory device of claim 1, whereineach metallic wall structure within the at least one vertical stackcontacts, and laterally surrounds, a respective inner dielectric spacer,and contacts, and is laterally surrounded by, a respective outerdielectric spacer having a same composition and a same thickness as therespective inner dielectric spacer.
 8. The three-dimensional memorydevice of claim 1, wherein: each of the memory stack structurescomprises a memory film and a vertical semiconductor channel, the memoryfilm including a respective vertical stack of memory elements; and eachmetallic wall structure within the at least one vertical stack protrudesabove a horizontal plane including top surfaces of the memory stackstructures.
 9. The three-dimensional memory device of claim 1, wherein:the first alternating stack comprises a first staircase region in whicha lateral extent of layers within the first alternating stack decreasesstepwise with an increase in a vertical distance from the semiconductorsubstrate; and the second alternating stack comprises a second staircaseregion in which a lateral extent of layers within the second alternatingstack decreases stepwise with an increase in the vertical distance fromthe semiconductor substrate.
 10. The three-dimensional memory device ofclaim 9, wherein the memory die comprises a retro-stepped dielectricmaterial portion that laterally encloses, and contacts, the firstalternating stack and is laterally enclosed by, and contacts, the secondalternating stack.
 11. The three-dimensional memory device of claim 1,wherein: the memory die has a rectangular horizontal cross-sectionalshape bounded by four straight sidewalls; and each respective metallicwall structure comprises four metallic wall segments that are parallelto a respective one of the four straight sidewalls.
 12. Thethree-dimensional memory device of claim 1, wherein: a total number ofthe first insulating layers in the first alternating stack is the sameas a total number of the second insulating layers in the secondalternating stack; and each first insulating layer in the firstalternating stack is vertically spaced from the semiconductor substrateby a same vertical distance as a respective one of the second insulatinglayers in the second alternating stack is from the semiconductorsubstrate.
 13. The three-dimensional memory device of claim 1, wherein:the first insulating layers and the second insulating layers comprisesilicon oxide; the electrically conductive layers comprise at least onemetallic material; and the spacer dielectric layers comprise siliconnitride.
 14. The three-dimensional memory device of claim 1, furthercomprising a support die bonded to the memory die, wherein the supportdie comprises: peripheral circuitry configured to control operation ofthe vertical stacks of memory elements; support-die bonding pads thatare bonded to the memory-die bonding pads; and support-die metalinterconnect structures electrically connecting nodes of the peripheralcircuitry to a respective one of the support-die bonding pads andincluded in support-die dielectric material layers.
 15. A method offorming a three-dimensional memory device, wherein the method comprisesforming a memory die using processing steps of: forming a verticallyalternating stack of insulating layers and dielectric spacer materiallayers over a semiconductor substrate; patterning the verticallyalternating stack into a first alternating stack of first insulatinglayers and sacrificial material layers and a second alternating stack ofsecond insulating layers and spacer dielectric layers, wherein thesecond alternating stack laterally encloses, and is laterally spacedfrom, the first alternating stack; forming memory stack structurescomprising vertical stacks of memory elements through the firstalternating stack; replacing the sacrificial material layers withelectrically conductive layers while retaining the second alternatingstack intact; forming at least one metallic wall structure verticallythrough the second alternating stack; forming memory-die bonding padswithin dielectric material layers over the first alternating stack; andforming an edge seal assembly comprising at least one vertical stack ofmetallic seal structures, wherein each of the at least one verticalstack of metallic seal structures vertically extends from a top surfaceof the semiconductor substrate to a bonding-side surface of thedielectric material layers, and comprises a respective one of the atleast one metallic wall structure.
 16. The method of claim 15, furthercomprising forming at least one bonding strip concurrently withformation of memory-die bonding pads, wherein: each of the at least onebonding strip laterally surrounds the memory-die bonding pads; and eachof the at least one vertical stack of metallic seal structures comprisesa respective memory-die bonding strip that laterally encloses thememory-die bonding pads.
 17. The method of claim 16, further comprisingforming upper-level metal interconnect structures in the dielectricmaterial layers, wherein each of the at least one vertical stack ofmetallic seal structures comprises a respective subset of theupper-level metal interconnect structures that extends between therespective metallic wall structure and the respective memory-die bondingpad.
 18. The method of claim 17, further comprising forming lower metalinterconnect structures within lower-level dielectric material layersover the semiconductor substrate, wherein the vertically alternatingstack is formed over the lower-level dielectric material layers, whereineach of the at least one vertical stack of metallic seal structurescomprises a respective subset of the lower metal interconnect structuresthat extends between the respective metallic wall structure and thesemiconductor substrate.
 19. The method of claim 15, wherein: the atleast one vertical stack of metallic seal structures comprises aplurality of vertical stacks of metallic seal structures; and each ofthe plurality of vertical stacks of metallic seal structures laterallysurrounds, or is laterally surrounded by, another vertical stack amongthe plurality of vertical stacks of metallic seal structures.
 20. Themethod of claim 15, further comprising: providing a support die thatcomprises: a peripheral circuit configured to control operation of thevertical stacks of memory elements, support-die bonding pads located ata bonding-side surface of support-die dielectric material layers thatoverlie the peripheral circuit, and support-die metal interconnectstructures electrically connecting nodes of the peripheral circuit to arespective one of the support-die bonding pads and included in thesupport-die dielectric material layers, and bonding the support-diebonding pads to the memory-die bonding pads.